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83 results on '"Zaki Leghtas"'

1. High-performance repetition cat code using fast noisy operations

Author: Francois-Marie Le Régent, Camille Berdou, Zaki Leghtas, Jérémie Guillaud, and Mazyar Mirrahimi
Subjects: Physics, QC1-999
Abstract: Bosonic cat qubits stabilized by two-photon driven dissipation benefit from exponential suppression of bit-flip errors and an extensive set of gates preserving this protection. These properties make them promising building blocks of a hardware-efficient and fault-tolerant quantum processor. In this paper, we propose a performance optimization of the repetition cat code architecture using fast but noisy CNOT gates for stabilizer measurements. This optimization leads to high thresholds for the physical figure of merit, given as the ratio between intrinsic single-photon loss rate of the bosonic mode and the engineered two-photon loss rate, as well as an improved scaling below threshold of the required overhead, to reach an expected level of logical error rate. Relying on the specific error models for cat qubit operations, this optimization exploits fast parity measurements, using accelerated low-fidelity CNOT gates, combined with fast ancilla parity-check qubits. The significant enhancement in the performance is explained by: 1- the highly asymmetric error model of cat qubit CNOT gates with a major component on control (ancilla) qubits, and 2- the robustness of the repetition cat code error correction performance in presence of the leakage induced by fast operations. In order to demonstrate these performances, we develop a method to sample the repetition code under circuit-level noise that also takes into account cat qubit state leakage.
Published: 2023
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2. Energy-participation quantization of Josephson circuits

Author: Zlatko K. Minev, Zaki Leghtas, Shantanu O. Mundhada, Lysander Christakis, Ioan M. Pop, and Michel H. Devoret
Subjects: Physics, QC1-999, Electronic computers. Computer science, QA75.5-76.95
Abstract: Abstract Superconducting microwave circuits incorporating nonlinear devices, such as Josephson junctions, are a leading platform for emerging quantum technologies. Increasing circuit complexity further requires efficient methods for the calculation and optimization of the spectrum, nonlinear interactions, and dissipation in multi-mode distributed quantum circuits. Here we present a method based on the energy-participation ratio (EPR) of a dissipative or nonlinear element in an electromagnetic mode. The EPR, a number between zero and one, quantifies how much of the mode energy is stored in each element. The EPRs obey universal constraints and are calculated from one electromagnetic-eigenmode simulation. They lead directly to the system quantum Hamiltonian and dissipative parameters. The method provides an intuitive and simple-to-use tool to quantize multi-junction circuits. We experimentally tested this method on a variety of Josephson circuits and demonstrated agreement within several percents for nonlinear couplings and modal Hamiltonian parameters, spanning five orders of magnitude in energy, across a dozen samples.
Published: 2021
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3. Multiplexed Photon Number Measurement

Author: Antoine Essig, Quentin Ficheux, Théau Peronnin, Nathanaël Cottet, Raphaël Lescanne, Alain Sarlette, Pierre Rouchon, Zaki Leghtas, and Benjamin Huard
Subjects: Physics, QC1-999
Abstract: When a two-level system—a qubit—is used as a probe of a larger system, it naturally leads to answering a single yes-no question about the system state. Here we propose a method where a single qubit is able to extract, not a single, but many bits of information about the photon number of a microwave resonator using continuous measurement. We realize a proof-of-principle experiment by recording the fluorescence emitted by a superconducting qubit reflecting a frequency comb, thus implementing multiplexed photon counting where the information about each Fock state—from 0 to 8—is simultaneously encoded in independent measurement channels. Direct Wigner tomography of the quantum state of the resonator evidences the backaction of the measurement as well as the optimal information extraction parameters. Our experiment unleashes the full potential of quantum meters by replacing sequential quantum measurements with simultaneous and continuous measurements separated in the frequency domain.
Published: 2021
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4. Irreversible Qubit-Photon Coupling for the Detection of Itinerant Microwave Photons

Author: Raphaël Lescanne, Samuel Deléglise, Emanuele Albertinale, Ulysse Réglade, Thibault Capelle, Edouard Ivanov, Thibaut Jacqmin, Zaki Leghtas, and Emmanuel Flurin
Subjects: Physics, QC1-999
Abstract: Single photon detection is a key resource for sensing at the quantum limit and the enabling technology for measurement-based quantum computing. Photon detection at optical frequencies relies on irreversible photoassisted ionization of various natural materials. However, microwave photons have energies 5 orders of magnitude lower than optical photons, and are therefore ineffective at triggering measurable phenomena at macroscopic scales. Here, we report the observation of a new type of interaction between a single two-level system (qubit) and a microwave resonator. These two quantum systems do not interact coherently; instead, they share a common dissipative mechanism to a cold bath: the qubit irreversibly switches to its excited state if and only if a photon enters the resonator. We have used this highly correlated dissipation mechanism to detect itinerant photons impinging on the resonator. This scheme does not require any prior knowledge of the photon waveform nor its arrival time, and dominant decoherence mechanisms do not trigger spurious detection events (dark counts). We demonstrate a detection efficiency of 58% and a record low dark count rate of 1.4 per millisecond. This work establishes engineered nonlinear dissipation as a key enabling resource for a new class of low-noise nonlinear microwave detectors.
Published: 2020
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5. Back and forth nudging for quantum state estimation by continuous weak measurement.

Author: Zaki Leghtas, Mazyar Mirrahimi, and Pierre Rouchon
Published: 2011
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6. Parameter estimation of a 3-level quantum system with a single population measurement.

Author: Zaki Leghtas, Mazyar Mirrahimi, and Pierre Rouchon
Published: 2009
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7. Vacuum-field-induced THz transport gap in a carbon nanotube quantum dot

Author: Audrey Cottet, Matthieu C. Dartiailh, Jérôme Tignon, Takis Kontos, M. M. Desjardins, L. C. Contamin, Matthieu R. Delbecq, Kazushi Yoshida, S. Massabeau, Kazuhiko Hirakawa, Juliette Mangeney, Tino Cubaynes, Zaki Leghtas, Sébastien Balibar, Simon Messelot, Sukhdeep Dhillon, Federico Valmorra, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institute of Industrial Science (IIS), The University of Tokyo (UTokyo), Physique Mésoscopique, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Nano-THz, Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Théorie de la Matière Condensée, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris)
Subjects: Photon, Electronic properties and materials, Band gap, Science, General Physics and Astronomy, Physics::Optics, 02 engineering and technology, Carbon nanotube, 7. Clean energy, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Article, law.invention, law, 0103 physical sciences, Spontaneous emission, 010306 general physics, Single photons and quantum effects, Quantum fluctuation, Physics, Quantum optics, [PHYS]Physics [physics], Multidisciplinary, business.industry, General Chemistry, 021001 nanoscience & nanotechnology, Carbon nanotube quantum dot, Quantum technology, Optoelectronics, 0210 nano-technology, business
Abstract: The control of light-matter interaction at the most elementary level has become an important resource for quantum technologies. Implementing such interfaces in the THz range remains an outstanding problem. Here, we couple a single electron trapped in a carbon nanotube quantum dot to a THz resonator. The resulting light-matter interaction reaches the deep strong coupling regime that induces a THz energy gap in the carbon nanotube solely by the vacuum fluctuations of the THz resonator. This is directly confirmed by transport measurements. Such a phenomenon which is the exact counterpart of inhibition of spontaneous emission in atomic physics opens the path to the readout of non-classical states of light using electrical current. This would be a particularly useful resource and perspective for THz quantum optics., Strong light-matter coupling has been realized at the level of single atoms and photons throughout most of the electromagnetic spectrum, except for the THz range. Here, the authors report a THz-scale transport gap, induced by vacuum fluctuations in carbon nanotube quantum dot through the deep strong coupling of a single electron to a THz resonator.
Published: 2021
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8. Hamiltonian Identification Through Enhanced Observability Utilizing Quantum Control.

Author: Zaki Leghtas, Gabriel Turinici, Herschel Rabitz, and Pierre Rouchon
Published: 2012
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9. Quantum control experiments as a testbed for evolutionary multi-objective algorithms.

Author: Ofer M. Shir, Jonathan Roslund, Zaki Leghtas, and Herschel Rabitz
Published: 2012
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10. Quantum Control Experiments as a Testbed for Evolutionary Multi-Objective Algorithms

Author: Ofer M. Shir, Jonathan Roslund, Zaki Leghtas, and Herschel Rabitz
Published: 2011

11. Theory of interactions between cavity photons induced by a mesoscopic circuit

Author: Zaki Leghtas, Audrey Cottet, Takis Kontos, Théorie de la Matière Condensée, Laboratoire de physique de l'ENS - ENS Paris (LPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), QUANTum Information Circuits (QUANTIC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Physique Mésoscopique, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Circuits Quantiques Hybrides, Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, and Université Paris sciences et lettres (PSL)
Subjects: Physics, Quantum Physics, Mesoscopic physics, Photon, Condensed Matter - Mesoscale and Nanoscale Physics, Lindblad equation, FOS: Physical sciences, Physics::Optics, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, 3. Good health, Quantum mechanics, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Dissipative system, Wigner distribution function, 010306 general physics, 0210 nano-technology, Quantum Physics (quant-ph), Quantum, Effective action, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Microwave cavity
Abstract: We use a quantum path integral approach to describe the behavior of a microwave cavity coupled to a dissipative mesoscopic circuit. We integrate out the mesoscopic electronic degrees of freedom to obtain a cavity effective action at fourth order in the light/matter coupling. By studying the structure of this action, we establish sufficient conditions in which the cavity dynamics can be described with a Lindblad equation. This equation depends on effective parameters set by electronic correlation functions. It reveals that the mesoscopic circuit induces an effective Kerr interaction and two-photon dissipative processes. We use our method to study the effective dynamics of a cavity coupled to a double quantum dot with normal metal reservoirs. If the cavity is driven at twice its frequency, the double dot circuit generates photonic squeezing and non-classicalities visible in the cavity Wigner function. In particular, we find a counterintuitive situation where mesoscopic dissipation enables the production of photonic Schr\"odinger cats. These effects can occur for realistic circuit parameters. Our method can be generalized straightforwardly to more complex circuit geometries with, for instance, multiple quantum dots, and other types of fermionic reservoirs such as superconductors and ferromagnets., Comment: 23 pages, 12 figures, submitted
Published: 2020
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12. Irreversible Qubit-Photon Coupling for the Detection of Itinerant Microwave Photons

Author: Edouard Ivanov, Zaki Leghtas, Thibault Capelle, Emmanuel Flurin, Raphaël Lescanne, Samuel Deléglise, Emanuele Albertinale, Ulysse Reglade, Thibaut Jacqmin, Laboratoire de Physique Théorique de l'ENS [École Normale Supérieure] (LPTENS), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), QUANTum Information Circuits (QUANTIC), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL), Laboratoire Kastler Brossel (LKB (Jussieu)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Quantronics Group (QUANTRONICS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre Automatique et Systèmes (CAS), Physique Mésoscopique, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Z. L. acknowledges support from the ANR grant ENDURANCE, and the EMERGENCES grant ENDURANCE of Ville de Paris. S. D. acknowledges support from the ANR grant QuNaT. E. I. acknowledges support from the European Union’s Horizon 2020 Programme for Research and Innovation under Grant Agreement No. 722923 (Marie Curie ETN-OMT). E. A. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 765267. The devices were fabricated within the consortium Salle Blanche Paris Centre. E. F. acknowledges support fromt he ENS Junior Research Chair under grant LabEX ENS-ICFP: No. ANR-10-LABX-0010 and No. ANR-10-IDEX-0001-02 PSL* and from the ANR grant DARKWADOR:ANR-19-CE47-0004. This work has been supported by the Paris Île-de-France Region in the framework of DIMSIRTEQ (Domaine d’intérêt majeur science et ingénierie en région Ile-de-France pour les technologies quantiques)., ANR-16-ACHN-0012,ENDURANCE,Processus multi-photons dans des circuits supraconducteurs pour la correction d'erreur quantique(2016), ANR-14-CE26-0002,QuNaT,Convertisseur Quantique Nanomécanique(2014), Laboratoire de Physique Théorique de l'ENS (LPTENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, and Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023))
Subjects: Physics, [PHYS]Physics [physics], Quantum decoherence, Photon, QC1-999, Quantum limit, General Physics and Astronomy, 01 natural sciences, 010305 fluids & plasmas, Resonator, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Qubit, 0103 physical sciences, Atomic physics, 010306 general physics, Quantum, Microwave, Quantum computer
Abstract: International audience; Single photon detection is a key resource for sensing at the quantum limit and the enabling technologyfor measurement-based quantum computing. Photon detection at optical frequencies relies on irreversiblephotoassisted ionization of various natural materials. However, microwave photons have energies 5 ordersof magnitude lower than optical photons, and are therefore ineffective at triggering measurable phenomenaat macroscopic scales. Here, we report the observation of a new type of interaction between a single two-level system (qubit) and a microwave resonator. These two quantum systems do not interact coherently;instead, they share a common dissipative mechanism to a cold bath: the qubit irreversibly switches to itsexcited state if and only if a photon enters the resonator. We have used this highly correlated dissipationmechanism to detect itinerant photons impinging on the resonator. This scheme does not require any priorknowledge of the photon waveform nor its arrival time, and dominant decoherence mechanisms do nottrigger spurious detection events (dark counts). We demonstrate a detection efficiency of 58% and a recordlow dark count rate of 1.4 per millisecond. This work establishes engineered nonlinear dissipation as a keyenabling resource for a new class of low-noise nonlinear microwave detectors.
Published: 2020
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13. Highly coherent spin states in carbon nanotubes coupled to cavity photons

Author: L. C. Contamin, Audrey Cottet, Takis Kontos, M. M. Desjardins, Laure Bruhat, Matthieu R. Delbecq, Matthieu C. Dartiailh, T. Cubaynes, Zaki Leghtas, Réouven Assouly, François Mallet, Physique Mésoscopique, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Université Paris Diderot - Paris 7 (UPD7)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Université Paris Diderot - Paris 7 (UPD7), Chalmers University of Technology [Göteborg], Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), QUANTum Information Circuits (QUANTIC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Théorie de la Matière Condensée, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Circuits Quantiques Hybrides, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL), ANR-17-ERC3-0005,FunTheme,Thermoélectricité fondamentale avec des circuits mésoscopiques(2017), European Project: 307778,EC:FP7:ERC,ERC-2012-StG_20111012,CIRQYS(2013), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, and École normale supérieure - Paris (ENS Paris)-MINES ParisTech - École nationale supérieure des mines de Paris-Sorbonne Université (SU)-Inria de Paris
Subjects: Photon, Quantum decoherence, Spin states, Computer Networks and Communications, FOS: Physical sciences, Carbon nanotube, 01 natural sciences, lcsh:QA75.5-76.95, 010305 fluids & plasmas, law.invention, law, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Computer Science (miscellaneous), 010306 general physics, ComputingMilieux_MISCELLANEOUS, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Microwave cavity, Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Spins, Quantum dots, Statistical and Nonlinear Physics, lcsh:QC1-999, Computational Theory and Mathematics, Quantum dot, Qubit, lcsh:Electronic computers. Computer science, Atomic physics, Qubits, lcsh:Physics
Abstract: Spins confined in quantum dots are considered as a promising platform for quantum information processing. While many advanced quantum operations have been demonstrated, experimental as well as theoretical efforts are now focusing on the development of scalable spin quantum bit architectures. One particularly promising method relies on the coupling of spin quantum bits to microwave cavity photons. This would enable the coupling of distant spins via the exchange of virtual photons for two qubit gate applications, which still remains to be demonstrated with spin qubits. Here, we use a circuit QED spin–photon interface to drive a single electronic spin in a carbon nanotube-based double quantum dot using cavity photons. The microwave spectroscopy allows us to identify an electrically controlled spin transition with a decoherence rate which can be tuned to be as low as 250 kHz. We show that this value is consistent with the expected hyperfine coupling in carbon nanotubes. These coherence properties, which can be attributed to the use of pristine carbon nanotubes stapled inside the cavity, should enable coherent spin–spin interaction via cavity photons and compare favorably to the ones recently demonstrated in Si-based circuit QED experiments. Our clean and controlled nano-assembly technique of carbon nanotubes in the cavity could be further improved by purified 12C growth to get rid of the nuclear spins resulting in an even higher spin coherence.
Published: 2019
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14. Exponential suppression of bit-flips in a qubit encoded in an oscillator

Author: Alain Sarlette, Matthieu R. Delbecq, Benjamin Huard, Raphaël Lescanne, Takis Kontos, Mazyar Mirrahimi, Zaki Leghtas, Marius Villiers, Théau Peronnin, Physique Mésoscopique, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), QUANTum Information Circuits (QUANTIC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Circuits Quantiques Hybrides, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris)
Subjects: Physics, Quantum Physics, Quantum decoherence, Technology and Engineering, Physical system, General Physics and Astronomy, FOS: Physical sciences, Topology, 01 natural sciences, STATE, 010305 fluids & plasmas, Physics and Astronomy, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum error correction, Qubit, Phase space, 0103 physical sciences, Quantum system, 010306 general physics, Quantum Physics (quant-ph), Quantum, QUANTUM, Quantum computer
Abstract: The choice of the physical system that represents a qubit can help reduce errors. Encoding them in the quadrature space of a superconducting resonator leads to exponentially reduced bit-flip rates, while phase-flip errors increase only linearly. A quantum system interacts with its environment-if ever so slightly-no matter how much care is put into isolating it(1). Therefore, quantum bits undergo errors, putting dauntingly difficult constraints on the hardware suitable for quantum computation(2). New strategies are emerging to circumvent this problem by encoding a quantum bit non-locally across the phase space of a physical system. Because most sources of decoherence result from local fluctuations, the foundational promise is to exponentially suppress errors by increasing a measure of this non-locality(3,4). Prominent examples are topological quantum bits, which delocalize information over real space and where spatial extent measures non-locality. Here, we encode a quantum bit in the field quadrature space of a superconducting resonator endowed with a special mechanism that dissipates photons in pairs(5,6). This process pins down two computational states to separate locations in phase space. By increasing this separation, we measure an exponential decrease of the bit-flip rate while only linearly increasing the phase-flip rate(7). Because bit-flips are autonomously corrected, only phase-flips remain to be corrected via a one-dimensional quantum error correction code. This exponential scaling demonstrates that resonators with nonlinear dissipation are promising building blocks for quantum computation with drastically reduced hardware overhead(8).
Published: 2019
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15. Structural Instability of Driven Josephson Circuits Prevented by an Inductive Shunt

Author: Michel Devoret, Zaki Leghtas, Raphaël Lescanne, Lucas Verney, Mazyar Mirrahimi, QUANTum Information Circuits (QUANTIC), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL), Laboratoire Pierre Aigrain (LPA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Departments of Applied Physics [New Haven], Yale University [New Haven], Centre Automatique et Systèmes (CAS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Yale Quantum Institute, MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris
Subjects: Superconductivity, Quantum information, FOS: Physical sciences, General Physics and Astronomy, 02 engineering and technology, Hardware_PERFORMANCEANDRELIABILITY, Topology, 01 natural sciences, Instability, Superconductivity (cond-mat.supr-con), [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, 010306 general physics, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Electronic circuit, Parametric statistics, Quantum computer, Physics, Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, Transmon, 021001 nanoscience & nanotechnology, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Complex dynamics, Qubit, Nonlinear dynamics, Quantum Physics (quant-ph), 0210 nano-technology, Shunt (electrical)
Abstract: Superconducting circuits are a versatile platform to implement a multitude of Hamiltonians which perform quantum computation, simulation and sensing tasks. A key ingredient for realizing a desired Hamiltonian is the irradiation of the circuit by a strong drive. These strong drives provide an in-situ control of couplings, which cannot be obtained by near-equilibrium Hamiltonians. However, as shown in this paper, out-of-equilibrium systems are easily plagued by complex dynamics leading to instabilities. Predicting and preventing these instabilities is crucial, both from a fundamental and application perspective. We propose an inductively shunted transmon as the elementary circuit optimized for strong parametric drives. Developing a novel numerical approach that avoids the built-in limitations of perturbative analysis, we demonstrate that adding the inductive shunt significantly extends the range of pump powers over which the circuit behaves in a stable manner., Comment: 11 pages, 7 figures
Published: 2019
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16. Escape of a Driven Quantum Josephson Circuit into Unconfined States

Author: Lucas Verney, Michel Devoret, Raphaël Lescanne, Quentin Ficheux, Mazyar Mirrahimi, Zaki Leghtas, Benjamin Huard, Laboratoire Pierre Aigrain (LPA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), QUANTum Information Circuits (QUANTIC), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Departments of Applied Physics [New Haven], Yale University [New Haven], Yale Quantum Institute, Centre Automatique et Systèmes (CAS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Chaotic, General Physics and Astronomy, 02 engineering and technology, Transmon, 021001 nanoscience & nanotechnology, 01 natural sciences, Instability, Nonlinear system, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum mechanics, Condensed Matter::Superconductivity, 0103 physical sciences, Quantum information, 010306 general physics, 0210 nano-technology, Quantum, Microwave, Electronic circuit
Abstract: International audience; Josephson circuits have been ideal systems with which to study complex nonlinear dynamics that can lead to chaotic behavior and instabilities. More recently, Josephson circuits in the quantum regime, particularly in the presence of microwave drives, have demonstrated their ability to emulate a variety of Hamiltonians that are useful for the processing of quantum information. In this paper, we show that these drives lead to an instability that results in the escape of the circuit mode into states that are not confined by the Josephson cosine potential. We observe this escape in a ubiquitous circuit: a transmon embedded in a 3D cavity. When the transmon occupies these free-particle-like states, the circuit behaves as though the junction had been removed and all nonlinearities are lost. This work deepens our understanding of strongly driven Josephson circuits, which is important for fundamental and application perspectives, such as the engineering of Hamiltonians by parametric pumping.
Published: 2019
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17. Dynamically protected cat-qubits: a new paradigm for universal quantum computation

Author: Mazyar Mirrahimi, Zaki Leghtas, Victor V Albert, Steven Touzard, Robert J Schoelkopf, Liang Jiang, and Michel H Devoret
Subjects: quantum superconducting circuits, circuit quantum electrodynamics, quantum error correction, quantum reservoir engineering, universal quantum computation, Science, Physics, QC1-999
Abstract: We present a new hardware-efficient paradigm for universal quantum computation which is based on encoding, protecting and manipulating quantum information in a quantum harmonic oscillator. This proposal exploits multi-photon driven dissipative processes to encode quantum information in logical bases composed of Schrödinger cat states. More precisely, we consider two schemes. In a first scheme, a two-photon driven dissipative process is used to stabilize a logical qubit basis of two-component Schrödinger cat states. While such a scheme ensures a protection of the logical qubit against the photon dephasing errors, the prominent error channel of single-photon loss induces bit-flip type errors that cannot be corrected. Therefore, we consider a second scheme based on a four-photon driven dissipative process which leads to the choice of four-component Schrödinger cat states as the logical qubit. Such a logical qubit can be protected against single-photon loss by continuous photon number parity measurements. Next, applying some specific Hamiltonians, we provide a set of universal quantum gates on the encoded qubits of each of the two schemes. In particular, we illustrate how these operations can be rendered fault-tolerant with respect to various decoherence channels of participating quantum systems. Finally, we also propose experimental schemes based on quantum superconducting circuits and inspired by methods used in Josephson parametric amplification, which should allow one to achieve these driven dissipative processes along with the Hamiltonians ensuring the universal operations in an efficient manner.
Published: 2014
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18. Author Correction: Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

Author: Quentin Ficheux, Benjamin Huard, Sébastien Jezouin, and Zaki Leghtas
Subjects: Physics, Multidisciplinary, Science, Dephasing, Dynamics (mechanics), General Physics and Astronomy, Quantum Physics, General Chemistry, Article, General Biochemistry, Genetics and Molecular Biology, Qubit, Quantum mechanics, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, lcsh:Q, Relaxation (approximation), lcsh:Science
Abstract: Decoherence originates from the leakage of quantum information into external degrees of freedom. For a qubit, the two main decoherence channels are relaxation and dephasing. Here, we report an experiment on a superconducting qubit where we retrieve part of the lost information in both of these channels. We demonstrate that raw averaging the corresponding measurement records provides a full quantum tomography of the qubit state where all three components of the effective spin-1/2 are simultaneously measured. From single realizations of the experiment, it is possible to infer the quantum trajectories followed by the qubit state conditioned on relaxation and/or dephasing channels. The incompatibility between these quantum measurements of the qubit leads to observable consequences in the statistics of quantum states. The high level of controllability of superconducting circuits enables us to explore many regimes from the Zeno effect to underdamped Rabi oscillations depending on the relative strengths of driving, dephasing, and relaxation., Information leaked by a quantum system into its environment causes decoherence but if it is recorded then it can be used to infer the quantum state. Ficheux et al. monitor the relaxation and dephasing of a qubit and show that this allows all three components of the qubit to be probed simultaneously.
Published: 2018
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19. Demonstration of an Effective Ultrastrong Coupling between Two Oscillators

Author: Benjamin Huard, Pérola Milman, Simone Felicetti, Thomas Coudreau, Zaki Leghtas, Danijela Marković, S. Fedortchenko, Sébastien Jezouin, Quentin Ficheux, Laboratoire Pierre Aigrain (LPA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre Automatique et Systèmes (CAS), PSL Research University (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris)-MINES ParisTech - École nationale supérieure des mines de Paris-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris)
Subjects: Physics, Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, FOS: Physical sciences, General Physics and Astronomy, Quantum simulator, 01 natural sciences, 010305 fluids & plasmas, [SPI.AUTO]Engineering Sciences [physics]/Automatic, Nonlinear system, Coupling (physics), [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Qubit, Quantum electrodynamics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Quantum Physics (quant-ph), 010306 general physics, Ground state, Quantum, Quantum fluctuation, Harmonic oscillator
Abstract: International audience; When the coupling rate between two quantum systems becomes as large as their characteristic frequencies, it induces dramatic effects on their dynamics and even on the nature of their ground state. The case of a qubit coupled to a harmonic oscillator in this ultrastrong coupling regime has been investigated theoretically and experimentally. Here, we explore the case of two harmonic oscillators in the ultrastrong coupling regime. Probing the properties of their ground state remains out of reach in natural implementations. Therefore, we have realized an analog quantum simulation of this coupled system by dual frequency pumping a nonlinear superconducting circuit. The pump amplitudes directly tune the effective coupling rate. We observe spectroscopic signature of a mode hybridization that is characteristic of the ultrastrong coupling. We experimentally demonstrate a key property of the ground state of this simulated ultrastrong coupling between modes by observing simultaneous single- and two-mode squeezing of the radiated field below vacuum fluctuations.
Published: 2018
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20. Exploring Ultrastrong Coupling Effects Using a Josephson Mixer

Author: S. Fedortchenko, Sébastien Jezouin, Pérola Milman, Simone Felicetti, Benjamin Huard, Danijela Marković, and Zaki Leghtas
Subjects: Coupling, Physics, Superconductivity, Computer Science::Hardware Architecture, Computer Science::Emerging Technologies, Superconducting circuits, Condensed matter physics, Condensed Matter::Superconductivity, Microwave, Harmonic oscillator
Abstract: Using superconducting circuits, we present an experimental simulation of the ultrastrong coupling between two harmonic oscillators.
Published: 2017
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21. Quantum simulation of a time-dependent ultrastrong coupling between two bosonic fields in circuit quantum electrodynamics

Author: Arne Keller, S. Fedortchenko, Simone Felicetti, Benjamin Huard, Zaki Leghtas, Sébastien Jezouin, Pérola Milman, Thomas Coudreau, and Danijela Marković
Subjects: Quantum technology, Physics, Coupling (physics), Open quantum system, Circuit quantum electrodynamics, Quantum electrodynamics, Quantum mechanics, Quantum dynamics, Cavity quantum electrodynamics, Quantum simulator, Noise (electronics)
Abstract: We propose a method that uses a superconducting architecture to simulate a time-dependent ultrastrong coupling between two bosonic fields. We show that the system emits microwave radiation with complex noise properties.
Published: 2017
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22. Robust Concurrent Remote Entanglement Between Two Superconducting Qubits

Author: Shantanu Mundhada, Robert Schoelkopf, Luigi Frunzio, Shyam Shankar, Michel Devoret, Wolfgang Pfaff, Zaki Leghtas, Anirudh Narla, Katrina Sliwa, Michael Hatridge, E. Zalys-Geller, Departments of Applied Physics [New Haven], Yale University [New Haven], Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC), Mines Paris - PSL (École nationale supérieure des mines de Paris), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Photon, QC1-999, FOS: Physical sciences, General Physics and Astronomy, 02 engineering and technology, Quantum entanglement, 01 natural sciences, [SPI.AUTO]Engineering Sciences [physics]/Automatic, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum mechanics, 0103 physical sciences, Communication methods, Quantum information, 010306 general physics, Quantum, Computer Science::Databases, Superconductivity, Physics, Quantum Physics, TheoryofComputation_GENERAL, 021001 nanoscience & nanotechnology, Qubit, Quantum Information, Quantum Physics (quant-ph), 0210 nano-technology, Microwave
Abstract: Entangling two remote quantum systems which never interact directly is an essential primitive in quantum information science and forms the basis for the modular architecture of quantum computing. When protocols to generate these remote entangled pairs rely on using traveling single photon states as carriers of quantum information, they can be made robust to photon losses, unlike schemes that rely on continuous variable states. However, efficiently detecting single photons is challenging in the domain of superconducting quantum circuits because of the low energy of microwave quanta. Here, we report the realization of a robust form of concurrent remote entanglement based on a novel microwave photon detector implemented in the superconducting circuit quantum electrodynamics (cQED) platform of quantum information. Remote entangled pairs with a fidelity of $0.57\pm0.01$ are generated at $200$ Hz. Our experiment opens the way for the implementation of the modular architecture of quantum computation with superconducting qubits., Main paper: 7 pages, 4 figures; Appendices: 14 pages, 9 figures
Published: 2016
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23. Extending the lifetime of a quantum bit with error correction in superconducting circuits

Author: Reinier Heeres, Yehan Liu, Mazyar Mirrahimi, Brian Vlastakis, Michel Devoret, Steven Girvin, Luigi Frunzio, Zaki Leghtas, Philip Reinhold, Robert Schoelkopf, Andrei Petrenko, Nissim Ofek, and Liang Jiang
Subjects: Multidisciplinary, Computer science, 02 engineering and technology, Transmon, 021001 nanoscience & nanotechnology, 01 natural sciences, Phase qubit, Quantum error correction, Quantum state, Qubit, Quantum mechanics, 0103 physical sciences, Quantum information, 010306 general physics, 0210 nano-technology, Error detection and correction, Algorithm, Quantum computer
Abstract: Quantum error correction (QEC) can overcome the errors experienced by qubits1 and is therefore an essential component of a future quantum computer. To implement QEC, a qubit is redundantly encoded in a higher-dimensional space using quantum states with carefully tailored symmetry properties. Projective measurements of these parity-type observables provide error syndrome information, with which errors can be corrected via simple operations2. The ‘break-even’ point of QEC—at which the lifetime of a qubit exceeds the lifetime of the constituents of the system—has so far remained out of reach3. Although previous works have demonstrated elements of QEC4–16, they primarily illustrate the signatures or scaling properties of QEC codes rather than test the capacity of the system to preserve a qubit over time. Here we demonstrate a QEC system that reaches the break-even point by suppressing the natural errors due to energy loss for a qubit logically encoded in superpositions of Schrodinger-cat states17 of a superconducting resonator18–21. We implement a full QEC protocol by using real-time feedback to encode, monitor naturally occurring errors, decode and correct. As measured by full process tomography, without any post-selection, the corrected qubit lifetime is 320 microseconds, which is longer than the lifetime of any of the parts of the system: 20 times longer than the lifetime of the transmon, about 2.2 times longer than the lifetime of an uncorrected logical encoding and about 1.1 longer than the lifetime of the best physical qubit (the |0〉f and |1〉f Fock states of the resonator). Our results illustrate the benefit of using hardware-efficient qubit encodings rather than traditional QEC schemes. Furthermore, they advance the field of experimental error correction from confirming basic concepts to exploring the metrics that drive system performance and the challenges in realizing a fault-tolerant system.
Published: 2016

24. Characterizing entanglement of an artificial atom and a cavity cat state with Bell’s inequality

Author: Michel Devoret, Michael Hatridge, Yehan Liu, Luigi Frunzio, Zaki Leghtas, K. Sliwa, Luyan Sun, Jacob Blumoff, Mazyar Mirrahimi, Brian Vlastakis, Robert Schoelkopf, Nissim Ofek, Liang Jiang, Andrei Petrenko, Departments of Applied Physics [New Haven], Yale University [New Haven], QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Physics, Bell state, Multidisciplinary, Cat state, General Physics and Astronomy, General Chemistry, Quantum entanglement, Quantum Physics, 01 natural sciences, Multipartite entanglement, General Biochemistry, Genetics and Molecular Biology, Article, 010305 fluids & plasmas, Local hidden variable theory, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], [MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], Quantum mechanics, 0103 physical sciences, Bell test experiments, GHZ experiment, 010306 general physics, Quantum teleportation
Abstract: The Schrodinger's cat thought experiment highlights the counterintuitive concept of entanglement in macroscopically distinguishable systems. The hallmark of entanglement is the detection of strong correlations between systems, most starkly demonstrated by the violation of a Bell inequality. No violation of a Bell inequality has been observed for a system entangled with a superposition of coherent states, known as a cat state. Here we use the Clauser–Horne–Shimony–Holt formulation of a Bell test to characterize entanglement between an artificial atom and a cat state, or a Bell-cat. Using superconducting circuits with high-fidelity measurements and real-time feedback, we detect correlations that surpass the classical maximum of the Bell inequality. We investigate the influence of decoherence with states up to 16 photons in size and characterize the system by introducing joint Wigner tomography. Such techniques demonstrate that information stored in superpositions of coherent states can be extracted efficiently, a crucial requirement for quantum computing with resonators., Qubit-cavity entanglement can be used for quantum information processing and for investigating the quantum-to-classical transition with high control. Here, the authors characterize the entanglement between an artificial atom and a cat state and its susceptibility to decoherence through Bell test witnesses.
Published: 2015
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25. Continuous generation and stabilization of mesoscopic field superposition states in a quantum circuit

Author: Mazyar Mirrahimi, Ananda L. Roy, Zaki Leghtas, Michel Devoret, A. Douglas Stone, QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Departments of Applied Physics [New Haven], Yale University [New Haven], Laboratoire Pierre Aigrain (LPA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre Automatique et Systèmes (CAS), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), École normale supérieure - Paris (ENS Paris), Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and MINES ParisTech - École nationale supérieure des mines de Paris
Subjects: Quantum decoherence, Photon, FOS: Physical sciences, Physics::Optics, 01 natural sciences, 010305 fluids & plasmas, [SPI.AUTO]Engineering Sciences [physics]/Automatic, Superconductivity (cond-mat.supr-con), Quantum circuit, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum state, Quantum mechanics, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Quantum, Quantum computer, Physics, Mesoscopic physics, Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, Cavity quantum electrodynamics, Atomic and Molecular Physics, and Optics, Quantum Physics (quant-ph)
Abstract: While dissipation is widely considered as being harmful for quantum coherence, it can, when properly engineered, lead to the stabilization of non-trivial pure quantum states. We propose a scheme for continuous generation and stabilization of Schr\"{o}dinger cat states in a cavity using dissipation engineering. We first generate non-classical photon states with definite parity by means of a two-photon drive and dissipation, and then stabilize these transient states against single-photon decay. The single-photon stabilization is autonomous, and is implemented through a second engineered bath, which exploits the photon number dependent frequency-splitting due to Kerr interactions in the strongly dispersive regime of circuit QED. Starting with the Hamiltonian of the baths plus cavity, we derive an effective model of only the cavity photon states along with analytic expressions for relevant physical quantities, such as the stabilization rate. The deterministic generation of such cat states is one of the key ingredients in performing universal quantum computation., Comment: 9 pages, 6 figures
Published: 2015

26. Planar multilayer circuit quantum electrodynamics

Author: Michael Hatridge, Robert Schoelkopf, Michel Devoret, Kyle Serniak, Katrina Sliwa, Zlatko Minev, Zaki Leghtas, Ioan Pop, Luigi Frunzio, Departments of Applied Physics [New Haven], Yale University [New Haven], QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris), and Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Aperture, General Physics and Astronomy, Physics::Optics, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Electromagnetic radiation, [SPI.AUTO]Engineering Sciences [physics]/Automatic, Superconductivity (cond-mat.supr-con), Resonator, Circuit quantum electrodynamics, Planar, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], 0103 physical sciences, 010306 general physics, Physics, Superconductivity, Quantum Physics, business.industry, Condensed Matter - Superconductivity, 021001 nanoscience & nanotechnology, Qubit, Physics::Accelerator Physics, Optoelectronics, 0210 nano-technology, business, Quantum Physics (quant-ph), Microfabrication
Abstract: International audience; Experimental quantum information processing with superconducting circuits is rapidly advancing, driven by innovation in two classes of devices, one involving planar microfabricated (2D) resonators, and the other involving machined three-dimensional (3D) cavities. We demonstrate that circuit quantum electrodynamics can be implemented in a multilayer superconducting structure that combines 2D and 3D advantages. We employ standard microfabrication techniques to pattern each layer, and rely on a vacuum gap between the layers to store the electromagnetic energy. Planar qubits are lithographically defined as an aperture in a conducting boundary of the resonators. We demonstrate the aperture concept by implementing an integrated, two-cavity-mode, one-transmon-qubit system.
Published: 2015
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27. Theory of remote entanglement via quantum-limited phase-preserving amplification

Author: E. Zalys-Geller, Michael Hatridge, Michel Devoret, Steven Girvin, Matti Silveri, Zaki Leghtas, Departments of Applied Physics [New Haven], Yale University [New Haven], QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Centre Automatique et Systèmes (CAS), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC), MINES ParisTech - École nationale supérieure des mines de Paris, École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris
Subjects: Physics, Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, FOS: Physical sciences, Concurrence, Quantum entanglement, Topology, 01 natural sciences, 010305 fluids & plasmas, law.invention, [SPI.AUTO]Engineering Sciences [physics]/Automatic, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], law, Qubit, Quantum mechanics, 0103 physical sciences, Master equation, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Heterodyne detection, W state, 010306 general physics, Quantum Physics (quant-ph), Quantum, Beam splitter
Abstract: We show that a quantum-limited phase-preserving amplifier can act as a which-path information eraser when followed by heterodyne detection. This 'beam splitter with gain' implements a continuous joint measurement on the signal sources. As an application, we propose heralded concurrent remote entanglement generation between two qubits coupled dispersively to separate cavities. Dissimilar qubit-cavity pairs can be made indistinguishable by simple engineering of the cavity driving fields providing further experimental flexibility and the prospect for scalability. Additionally, we find an analytic solution for the stochastic master equation, a quantum filter, yielding a thorough physical understanding of the nonlinear measurement process leading to an entangled state of the qubits. We determine the concurrence of the entangled states and analyze its dependence on losses and measurement inefficiencies., Comment: Main text (11 pages, 5 figures), updated to the published version
Published: 2015
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28. Tracking photon jumps with repeated quantum non-demolition parity measurements

Author: Michel Devoret, Robert Schoelkopf, Michael Hatridge, Andrei Petrenko, A. Narla, Luyan Sun, Shyam Shankar, Mazyar Mirrahimi, K. Sliwa, Brian Vlastakis, Jacob Blumoff, Gerhard Kirchmair, Zaki Leghtas, Luigi Frunzio, Departments of Applied Physics [New Haven], Yale University [New Haven], QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Physics, Quantum Physics, Quantum network, Multidisciplinary, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, FOS: Physical sciences, Quantum capacity, Quantum channel, 01 natural sciences, 010305 fluids & plasmas, Superconductivity (cond-mat.supr-con), Open quantum system, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum error correction, Quantum mechanics, Qubit, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum algorithm, Quantum information, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Quantum Physics (quant-ph), ComputingMilieux_MISCELLANEOUS
Abstract: Quantum error correction (QEC) is required for a practical quantum computer because of the fragile nature of quantum information. In QEC, information is redundantly stored in a large Hilbert space and one or more observables must be monitored to reveal the occurrence of an error, without disturbing the information encoded in an unknown quantum state. Such observables, typically multi-qubit parities such as , must correspond to a special symmetry property inherent to the encoding scheme. Measurements of these observables, or error syndromes, must also be performed in a quantum non-demolition (QND) way and faster than the rate at which errors occur. Previously, QND measurements of quantum jumps between energy eigenstates have been performed in systems such as trapped ions, electrons, cavity quantum electrodynamics (QED), nitrogen-vacancy (NV) centers, and superconducting qubits. So far, however, no fast and repeated monitoring of an error syndrome has been realized. Here, we track the quantum jumps of a possible error syndrome, the photon number parity of a microwave cavity, by mapping this property onto an ancilla qubit. This quantity is just the error syndrome required in a recently proposed scheme for a hardware-efficient protected quantum memory using Schr\"{o}dinger cat states in a harmonic oscillator. We demonstrate the projective nature of this measurement onto a parity eigenspace by observing the collapse of a coherent state onto even or odd cat states. The measurement is fast compared to the cavity lifetime, has a high single-shot fidelity, and has a 99.8% probability per single measurement of leaving the parity unchanged. In combination with the deterministic encoding of quantum information in cat states realized earlier, our demonstrated QND parity tracking represents a significant step towards implementing an active system that extends the lifetime of a quantum bit., Comment: 6 pages with 4 figures for the main text, 14 pages with 9 figures for supplementary material
Published: 2014
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29. Dynamically protected cat-qubits: a new paradigm for universal quantum computation

Author: Michel Devoret, Liang Jiang, Steven Touzard, Victor V. Albert, Robert Schoelkopf, Mazyar Mirrahimi, Zaki Leghtas, QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Yale University [New Haven], École normale supérieure - Paris (ENS-PSL), and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Quantum decoherence, General Physics and Astronomy, FOS: Physical sciences, Topology, 01 natural sciences, 010305 fluids & plasmas, Superconductivity (cond-mat.supr-con), symbols.namesake, Quantum gate, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum information, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Quantum, ComputingMilieux_MISCELLANEOUS, Quantum computer, Physics, Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, Quantum harmonic oscillator, Qubit, symbols, Quantum Physics (quant-ph), Schrödinger's cat
Abstract: We present a new hardware-efficient paradigm for universal quantum computation which is based on encoding, protecting and manipulating quantum information in a quantum harmonic oscillator. This proposal exploits multi-photon driven dissipative processes to encode quantum information in logical bases composed of Schr\"odinger cat states. More precisely, we consider two schemes. In a first scheme, a two-photon driven dissipative process is used to stabilize a logical qubit basis of two-component Schr\"odinger cat states. While such a scheme ensures a protection of the logical qubit against the photon dephasing errors, the prominent error channel of single-photon loss induces bit-flip type errors that cannot be corrected. Therefore, we consider a second scheme based on a four-photon driven dissipative process which leads to the choice of four-component Schr\"odinger cat states as the logical qubit. Such a logical qubit can be protected against single-photon loss by continuous photon number parity measurements. Next, applying some specific Hamiltonians, we provide a set of universal quantum gates on the encoded qubits of each of the two schemes. In particular, we illustrate how these operations can be rendered fault-tolerant with respect to various decoherence channels of participating quantum systems. Finally, we also propose experimental schemes based on quantum superconducting circuits and inspired by methods used in Josephson parametric amplification, which should allow to achieve these driven dissipative processes along with the Hamiltonians ensuring the universal operations in an efficient manner., Comment: 28 pages, 11 figures
Published: 2014
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30. Confining the state of light to a quantum manifold by engineered two-photon loss

Author: Ioan Pop, Shyam Shankar, Angela Kou, Luigi Frunzio, Robert Schoelkopf, Andrei Petrenko, Mazyar Mirrahimi, Brian Vlastakis, Katrina Sliwa, Michael Hatridge, Anirudh Narla, Zaki Leghtas, Matthew Reagor, Michel Devoret, Steven Touzard, Departments of Applied Physics [New Haven], Yale University [New Haven], QUANTum Information Circuits (QUANTIC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Physics, Quantum optics, Quantum Physics, Multidisciplinary, Photon, FOS: Physical sciences, Quantum entanglement, symbols.namesake, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum state, [MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], Qubit, Quantum mechanics, symbols, Coherent states, Quantum information, Quantum Physics (quant-ph), Schrödinger's cat
Abstract: Physical systems usually exhibit quantum behavior, such as superpositions and entanglement, only when they are sufficiently decoupled from a lossy environment. Paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. This notion can be generalized to the confinement of a system into a manifold of quantum states, consisting of all coherent superpositions of multiple stable steady states. We have experimentally confined the state of a harmonic oscillator to the quantum manifold spanned by two coherent states of opposite phases. In particular, we have observed a Schrodinger cat state spontaneously squeeze out of vacuum, before decaying into a classical mixture. This was accomplished by designing a superconducting microwave resonator whose coupling to a cold bath is dominated by photon pair exchange. This experiment opens new avenues in the fields of nonlinear quantum optics and quantum information, where systems with multi-dimensional steady state manifolds can be used as error corrected logical qubits.
Published: 2014
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31. Quantum reservoir engineering and single qubit cooling

Author: Uri Vool, Zaki Leghtas, Mazyar Mirrahimi, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Yale University [New Haven], and Sophie Tarbouriech and Miroslav Krstic
Subjects: General Medicine, Quantum capacity, One-way quantum computer, 01 natural sciences, Stabilization, 010305 fluids & plasmas, Bilinear Systems, Control theory, Quantum error correction, Quantum state, Qubit, 0103 physical sciences, Quantum operation, Quantum algorithm, 010306 general physics, Quantum information science, Dissipativity, Mathematics
Abstract: International audience; Stabilizing a quantum system in a desired state has important implications in quantum information science. In control engineering, stabilization is usually achieved by the use of feedback. The closed-loop control paradigm consists of measuring the system in a non-destructive manner, analyzing in real-time the measurement output to estimate the dynamical state and finally, calculating a feedback law to stabilize the desired state. However, the rather short dynamical time-scales of most quantum systems impose important limitations on the complexity of real-time output signal analysis and retroaction. An alternative control approach for quantum state stabilization, bypassing a real-time analysis of output signal, is called reservoir engineering. In this paper, we start with a general description of quantum reservoir engineering. We then apply this method to stabilize the ground state (lowest energy state) of a single two-level quantum system. Applying the averaging theorem and some simple Lyapunov techniques, we prove the convergence of our proposed scheme. This scheme has recently been successfully implemented on a superconducting qubit and has led to a fast and reliable reset protocol for these qubits
Published: 2013
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32. Stabilizing a Bell state of two superconducting qubits by dissipation engineering

Author: Michel Devoret, Shyam Shankar, Mazyar Mirrahimi, Zaki Leghtas, Michael Hatridge, Uri Vool, Steven Girvin, Yale University [New Haven], SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)
Subjects: Physics, Quantum Physics, Bell state, Cluster state, FOS: Physical sciences, Quantum entanglement, 01 natural sciences, Atomic and Molecular Physics, and Optics, 010305 fluids & plasmas, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Superdense coding, Quantum mechanics, Qubit, 0103 physical sciences, W state, Quantum Physics (quant-ph), 010306 general physics, Quantum teleportation, No-communication theorem
Abstract: We propose a dissipation engineering scheme that prepares and protects a maximally entangled state of a pair of superconducting qubits. This is done by off-resonantly coupling the two qubits to a low-Q cavity mode playing the role of a dissipative reservoir. We engineer this coupling by applying six continuous-wave microwave drives with appropriate frequencies. The two qubits need not be identical. We show that our approach does not require any fine-tuning of the parameters and requires only that certain ratios between them be large. With currently achievable coherence times, simulations indicate that a Bell state can be maintained over arbitrary long times with fidelities above 94%. Such performance leads to a significant violation of Bell's inequality (CHSH correlation larger than 2.6) for arbitrary long times., Comment: 5 pages, 4 figures
Published: 2013
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33. Manipulating Quantum Pathways on the Fly

Author: Zaki Leghtas, Herschel Rabitz, and Roberto Rey-de-Castro
Subjects: Physics, Fist, General Physics and Astronomy, Observable, Expectation value, Laser, law.invention, symbols.namesake, law, Quantum mechanics, Femtosecond, symbols, Quantum system, Hamiltonian (quantum mechanics), Quantum
Abstract: The expectation value of a quantum system observable can be written as a sum over interfering pathway amplitudes. In this Letter, we demonstrate for the fist time adaptive manipulation of quantum pathways using the Hamiltonian encoding-observable decoding (HE-OD) technique. The principles of HE-OD are illustrated for population transfer in atomic rubidium using shaped femtosecond laser pulses. The ability to manipulate multiple pathway amplitudes is of fundamental importance in all quantum control applications.
Published: 2013
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34. Deterministic protocol for mapping a qubit to coherent state superpositions in a cavity

Author: Robert Schoelkopf, Gerhard Kirchmair, Zaki Leghtas, Michel Devoret, Mazyar Mirrahimi, Brian Vlastakis, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Departments of Applied Physics [New Haven], and Yale University [New Haven]
Subjects: Physics, Quantum Physics, Flux qubit, Charge qubit, Cavity quantum electrodynamics, FOS: Physical sciences, 01 natural sciences, Atomic and Molecular Physics, and Optics, 010305 fluids & plasmas, Phase qubit, Computer Science::Emerging Technologies, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Controlled NOT gate, Quantum mechanics, Qubit, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], 0103 physical sciences, Coherent states, Quantum Physics (quant-ph), 010306 general physics, Quantum computer
Abstract: International audience; We introduce a new gate that transfers an arbitrary state of a qubit into a superposition of two quasi-orthogonal coherent states of a cavity mode, with opposite phases. This qcMAP gate is based on conditional qubit and cavity operations exploiting the energy level dispersive shifts, in the regime where they are much stronger than the cavity and qubit linewidths. The generation of multi-component superpositions of quasi-orthogonal coherent states, non-local entangled states of two resonators and multi-qubit GHZ states can be efficiently achieved by this gate.
Published: 2013

35. Hardware-efficient autonomous quantum memory protection

Author: Robert Schoelkopf, Michel Devoret, Gerhard Kirchmair, Mazyar Mirrahimi, Brian Vlastakis, Zaki Leghtas, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), and Yale University [New Haven]
Subjects: Physics, Quantum network, General Physics and Astronomy, Quantum capacity, Quantum channel, 01 natural sciences, 010305 fluids & plasmas, Circuit quantum electrodynamics, Quantum error correction, Qubit, Quantum mechanics, 0103 physical sciences, Electronic engineering, Quantum algorithm, Quantum information, 010306 general physics
Abstract: International audience; We propose to encode a quantum bit of information in a superposition of coherent states of an oscillator, with four different phases. Our encoding in a single cavity mode, together with a protection protocol, significantly reduces the error rate due to photon loss. This protection is ensured by an efficient quantum error correction scheme employing the nonlinearity provided by a single physical qubit coupled to the cavity. We describe in detail how to implement these operations in a circuit quantum electrodynamics system. This proposal directly addresses the task of building a hardware-efficient quantum memory and can lead to important shortcuts in quantum computing architectures.
Published: 2013
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36. Autonomously stabilized entanglement between two superconducting quantum bits

Author: Michael Hatridge, Steven Girvin, Mazyar Mirrahimi, Shyam Shankar, K. Sliwa, A. Narla, Uri Vool, Michel Devoret, Luigi Frunzio, Zaki Leghtas, Yale University [New Haven], SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)
Subjects: Physics, [PHYS]Physics [physics], Quantum network, Bell state, Multidisciplinary, Quantum Physics, One-way quantum computer, Topology, 01 natural sciences, 010305 fluids & plasmas, Open quantum system, Quantum error correction, Qubit, Quantum mechanics, 0103 physical sciences, Quantum information, 010306 general physics, Quantum teleportation, ComputingMilieux_MISCELLANEOUS
Abstract: An entangled Bell state of two superconducting quantum bits can be stabilized for an arbitrary time using an autonomous feedback scheme, that is, one that does not require a complicated external error-correcting feedback loop. Entangled states are a key resource in fundamental quantum physics, quantum cryptography and quantum computation. It has been generally assumed that the creation of such states requires the avoidance of contact with a dissipative environment, and minimization of decoherence. Some studies have shown, however, that dissipative interactions can be used to preserve coherence, and in this issue of Nature two groups demonstrate this principle for continuously driven physical systems. Lin et al. use engineered dissipation to deterministically produce and stabilize entanglement between two trapped-ion qubits, independent of their initial state. Shankar et al. use an autonomous feedback scheme to counteract decoherence and demonstrate the stabilization of an entangled Bell state of a quantum register of two superconducting qubits for an arbitrary time. This approach may be applied to a broad range of experimental systems to achieve desired quantum dynamics or steady states. Quantum error correction codes are designed to protect an arbitrary state of a multi-qubit register from decoherence-induced errors1, but their implementation is an outstanding challenge in the development of large-scale quantum computers. The first step is to stabilize a non-equilibrium state of a simple quantum system, such as a quantum bit (qubit) or a cavity mode, in the presence of decoherence. This has recently been accomplished using measurement-based feedback schemes2,3,4,5. The next step is to prepare and stabilize a state of a composite system6,7,8. Here we demonstrate the stabilization of an entangled Bell state of a quantum register of two superconducting qubits for an arbitrary time. Our result is achieved using an autonomous feedback scheme that combines continuous drives along with a specifically engineered coupling between the two-qubit register and a dissipative reservoir. Similar autonomous feedback techniques have been used for qubit reset9, single-qubit state stabilization10, and the creation11 and stabilization6 of states of multipartite quantum systems. Unlike conventional, measurement-based schemes, the autonomous approach uses engineered dissipation to counteract decoherence12,13,14,15, obviating the need for a complicated external feedback loop to correct errors. Instead, the feedback loop is built into the Hamiltonian such that the steady state of the system in the presence of drives and dissipation is a Bell state, an essential building block for quantum information processing. Such autonomous schemes, which are broadly applicable to a variety of physical systems, as demonstrated by the accompanying paper on trapped ion qubits16, will be an essential tool for the implementation of quantum error correction.
Published: 2013
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37. Observation of quantum state collapse and revival due to the single-photon Kerr effect

Author: Mazyar Mirrahimi, Brian Vlastakis, Robert Schoelkopf, Eran Ginossar, Gerhard Kirchmair, Zaki Leghtas, Simon E. Nigg, Hanhee Paik, Luigi Frunzio, Steven Girvin, Yale University [New Haven], SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)
Subjects: Quantum optics, Physics, Quantum Physics, Multidisciplinary, Condensed Matter - Superconductivity, Quantum sensor, Cavity quantum electrodynamics, FOS: Physical sciences, Physics::Optics, 01 natural sciences, 3. Good health, 010305 fluids & plasmas, Superconductivity (cond-mat.supr-con), Open quantum system, [MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], Quantum mechanics, Quantum process, Qubit, 0103 physical sciences, Coherent states, Quantum information, Quantum Physics (quant-ph), 010306 general physics
Abstract: Photons are ideal carriers for quantum information as they can have a long coherence time and can be transmitted over long distances. These properties are a consequence of their weak interactions within a nearly linear medium. To create and manipulate nonclassical states of light, however, one requires a strong, nonlinear interaction at the single photon level. One approach to generate suitable interactions is to couple photons to atoms, as in the strong coupling regime of cavity QED systems. In these systems, however, one only indirectly controls the quantum state of the light by manipulating the atoms. A direct photon-photon interaction occurs in so-called Kerr media, which typically induce only weak nonlinearity at the cost of significant loss. So far, it has not been possible to reach the single-photon Kerr regime, where the interaction strength between individual photons exceeds the loss rate. Here, using a 3D circuit QED architecture, we engineer an artificial Kerr medium which enters this regime and allows the observation of new quantum effects. We realize a Gedankenexperiment proposed by Yurke and Stoler, in which the collapse and revival of a coherent state can be observed. This time evolution is a consequence of the quantization of the light field in the cavity and the nonlinear interaction between individual photons. During this evolution non-classical superpositions of coherent states, i.e. multi-component Schroedinger cat states, are formed. We visualize this evolution by measuring the Husimi Q-function and confirm the non-classical properties of these transient states by Wigner tomography. The single-photon Kerr effect could be employed in QND measurement of photons, single photon generation, autonomous quantum feedback schemes and quantum logic operations., 6 pages, 4 figures, 5 pages supplementary Material, 3 figures
Published: 2013
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38. Deterministically encoding quantum information using 100-photon Schrödinger cat states

Author: Robert Schoelkopf, Gerhard Kirchmair, Simon E. Nigg, Michel Devoret, Zaki Leghtas, Mazyar Mirrahimi, Brian Vlastakis, Steven Girvin, Luigi Frunzio, Yale University [New Haven], SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)
Subjects: Physics, Multidisciplinary, Charge qubit, Quantum superposition, Cat state, Transmon, 01 natural sciences, 010305 fluids & plasmas, Phase qubit, Qubit, Quantum mechanics, 0103 physical sciences, Quantum information, 010306 general physics, Quantum computer
Abstract: Coherently Controlling Large Cats The control and manipulation of quantum information based on superconducting circuits is an attractive route because of the possibility of scale-up. Vlastakis et al. (p. 607 , published online 26 September; see the Perspective by Leek ) were able to generate and control quantum entanglement between a superconducting qubit and hundreds of photons stored in a cavity resonator by using deterministic methods for on-demand generation of large Schrödinger cat states in a microwave cavity with arbitrary size and phase. The ability to map the state of a qubit to large Schrödinger cat states should provide a robust quantum resource in future quantum-based technologies.
Published: 2013
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39. Demonstrating a driven reset protocol for a superconducting qubit

Author: Shyam Shankar, Zaki Leghtas, K. Geerlings, Robert Schoelkopf, Michel Devoret, Mazyar Mirrahimi, Luigi Frunzio, Ioan Pop, Departments of Applied Physics [New Haven], Yale University [New Haven], SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)
Subjects: Flux qubit, Charge qubit, Population, General Physics and Astronomy, FOS: Physical sciences, 02 engineering and technology, Topology, 01 natural sciences, Phase qubit, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Quantum mechanics, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum information, 010306 general physics, education, Physics, Quantum Physics, education.field_of_study, Condensed Matter - Mesoscale and Nanoscale Physics, Transmon, 021001 nanoscience & nanotechnology, Qubit, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], 0210 nano-technology, Quantum Physics (quant-ph), Reset (computing)
Abstract: Qubit reset is crucial at the start of and during quantum information algorithms. We present the experimental demonstration of a practical method to force qubits into their ground state, based on driving certain qubit and cavity transitions. Our protocol, called the double drive reset of population is tested on a superconducting transmon qubit in a three-dimensional cavity. Using a new method for measuring population, we show that we can prepare the ground state with a fidelity of at least 99.5 % in less than 3 microseconds; faster times and higher fidelity are predicted upon parameter optimization., Comment: 5 pages, 4 figures
Published: 2012
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40. Hamiltonian identification through enhanced observability utilizing quantum control

Author: Herschel Rabitz, Zaki Leghtas, Pierre Rouchon, Gabriel Turinici, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), CEntre de REcherches en MAthématiques de la DEcision (CEREMADE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Dauphine-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Department of Chemistry, Princeton University, Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris Dauphine-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: 0209 industrial biotechnology, Hamiltonian identification, [MATH.MATH-DS]Mathematics [math]/Dynamical Systems [math.DS], FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, symbols.namesake, 020901 industrial engineering & automation, Ramsey interferometry, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], 0103 physical sciences, Quantum system, Observability, Statistical physics, Electrical and Electronic Engineering, 010306 general physics, Quantum, Physics, Quantum Physics, Observable, Quantum control, Computer Science Applications, Arbitrarily large, Dipole, Control and Systems Engineering, symbols, [MATH.MATH-OC]Mathematics [math]/Optimization and Control [math.OC], Quantum Physics (quant-ph), Hamiltonian (quantum mechanics)
Abstract: This paper considers Hamiltonian identification for a controllable quantum system with non-degenerate transitions and a known initial state. We assume to have at our disposal a single scalar control input and the population measure of only one state at an (arbitrarily large) final time T. We prove that the quantum dipole moment matrix is locally observable in the following sense: for any two close but distinct dipole moment matrices, we construct discriminating controls giving two different measurements. Such discriminating controls are constructed to have three well defined temporal components, as inspired by Ramsey interferometry. This result suggests that what may appear at first to be very restrictive measurements are actually rich for identification, when combined with well designed discriminating controls, to uniquely identify the complete dipole moment of such systems. The assessment supports the employment of quantum control as a promising means to achieve high quality identification of a Hamiltonian., Submitted to IEEE TAC special issue on quantum control
Published: 2012
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41. Stabilization of nonclassical states of one- and two-mode radiation fields by reservoir engineering

Author: Zaki Leghtas, Alain Sarlette, Jean-Michel Raimond, Michel Brune, Pierre Rouchon, Department of Electrical Engineering and Computer Science (Institut Montefiore), Université de Liège, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Laboratoire Kastler Brossel (LKB (Lhomond)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: DECOHERENCE, Technology and Engineering, Quantum decoherence, FOS: Physical sciences, 01 natural sciences, [SPI.AUTO]Engineering Sciences [physics]/Automatic, 010309 optics, symbols.namesake, PROPOSAL, Circuit quantum electrodynamics, Quantum mechanics, 0103 physical sciences, SUPERPOSITIONS, 010306 general physics, Quantum, Microwave cavity, Physics, Quantum Physics, Mesoscopic physics, Cavity quantum electrodynamics, ATOM, DRIVEN, Atomic and Molecular Physics, and Optics, TRAPPED IONS, Reservoir engineering, CAVITY, symbols, OPTICS, Hamiltonian (quantum mechanics), Quantum Physics (quant-ph), QUANTUM, GENERATION
Abstract: We analyze a quantum reservoir engineering method, originally introduced by [Sarlette et al. in Phys. Rev. Lett. 107, 010402 (2011) -- arXiv 1011.5057], for the stabilization of non-classical field states in high quality cavities. We generalize the method to the protection of mesoscopic entangled field states shared by two non-degenerate field modes. The reservoir is made up of a stream of atoms undergoing successive composite interactions with the cavity, each combining resonant with non-resonant parts. We get a detailed insight into the competition between the engineered reservoir and decoherence. We show that the operation is quite insensitive to experimental imperfections and that it could thus be implemented in the near future, either in the context of microwave Cavity Quantum Electrodynamics or in that of circuit-QED., Comment: submitted to Physical Review A
Published: 2012
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42. Quantum Control Experiments as a Testbed for Evolutionary Multi-Objective Algorithms

Author: Jonathan Roslund, Ofer M. Shir, Herschel Rabitz, and Zaki Leghtas
Subjects: FOS: Computer and information sciences, Mathematical optimization, Quantum Physics, Computer science, Testbed, I.2.8, Pareto principle, Macroscopic quantum phenomena, FOS: Physical sciences, Computer Science - Neural and Evolutionary Computing, Context (language use), Mathematical Physics (math-ph), Multi-objective optimization, Computer Science Applications, Theoretical Computer Science, Domain (software engineering), Hardware and Architecture, Neural and Evolutionary Computing (cs.NE), CMA-ES, Evolution strategy, Quantum Physics (quant-ph), Software, Mathematical Physics
Abstract: Experimental multi-objective Quantum Control is an emerging topic within the broad physics and chemistry applications domain of controlling quantum phenomena. This realm offers cutting edge ultrafast laser laboratory applications, which pose multiple objectives, noise, and possibly constraints on the high-dimensional search. In this study we introduce the topic of multi-observable quantum control (MOQC), and consider specific systems to be Pareto optimized subject to uncertainty, either experimentally or by means of simulated systems. The latter include a family of mathematical test-functions with a practical link to MOQC experiments, which are introduced here for the first time. We investigate the behavior of the multi-objective version of the covariance aatrix adaptation evolution strategy (MO-CMA-ES) and assess its performance on computer simulations as well as on laboratory closed-loop experiments. Overall, we propose a comprehensive study on experimental evolutionary Pareto optimization in high-dimensional continuous domains, draw some practical conclusions concerning the impact of fitness disturbance on algorithmic behavior, and raise several theoretical issues in the broad evolutionary multi-objective context.
Published: 2011

43. Adiabatic passage and ensemble control of quantum systems

Author: Zaki Leghtas, Alain Sarlette, Pierre Rouchon, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Department of Electrical Engineering and Computer Science (Institut Montefiore), Université de Liège, Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), and Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: Physics, Quantum Physics, 0209 industrial biotechnology, FOS: Physical sciences, 02 engineering and technology, Condensed Matter Physics, 01 natural sciences, Atomic and Molecular Physics, and Optics, Pulse (physics), [SPI.AUTO]Engineering Sciences [physics]/Automatic, Permutation, 020901 industrial engineering & automation, Robustness (computer science), Excited state, 0103 physical sciences, Statistical physics, Quantum Physics (quant-ph), 010306 general physics, Adiabatic process, Ground state, Quantum, Eigenvalues and eigenvectors
Abstract: This paper considers population transfer between eigenstates of a finite quantum ladder controlled by a classical electric field. Using an appropriate change of variables, we show that this setting can be set in the framework of adiabatic passage, which is known to facilitate ensemble control of quantum systems. Building on this insight, we present a mathematical proof of robustness for a control protocol -- chirped pulse -- practiced by experimentalists to drive an ensemble of quantum systems from the ground state to the most excited state. We then propose new adiabatic control protocols using a single chirped and amplitude shaped pulse, to robustly perform any permutation of eigenstate populations, on an ensemble of systems with badly known coupling strengths. Such adiabatic control protocols are illustrated by simulations achieving all 24 permutations for a 4-level ladder.
Published: 2011
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44. Back and forth nudging for quantum state estimation by continuous weak measurement

Author: Pierre Rouchon, Mazyar Mirrahimi, Zaki Leghtas, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Centre Automatique et Systèmes (CAS), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), and Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: 0209 industrial biotechnology, Observer (quantum physics), Estimation theory, Estimator, Observable, 02 engineering and technology, 01 natural sciences, [SPI.AUTO]Engineering Sciences [physics]/Automatic, 020901 industrial engineering & automation, Control theory, Quantum state, 0103 physical sciences, Quantum system, Applied mathematics, Weak measurement, 010306 general physics, Mathematics, Quantum computer
Abstract: International audience; We propose to apply the Back and Forth Nudging (BFN) method used for geophysical data assimilations [1] to estimate the initial state of a quantum system. We consider a cloud of atoms interacting with a magnetic field while a single observable is being continuously measured over time using homodyne detection. The BFN method relies on designing an observer forward and backwards in time. The state of the BFN observer is continuously updated by the measured data and tends to converge to the system's state. The proposed estimator seems to be globally asymptotically convergent when the system is observable. A detailed convergence proof and simulations are given in the 2-level case. An extension of the algorithm to the multilevel case is also presented.
Published: 2011

45. Parameter estimation of a 3-level quantum system with a single population measurement

Author: Pierre Rouchon, Mazyar Mirrahimi, Zaki Leghtas, SIgnals and SYstems in PHysiology & Engineering (SISYPHE), Inria Paris-Rocquencourt, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Centre Automatique et Systèmes (CAS), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), ANR-06-BLAN-0052,C-QUID,Contrôle et identification de systèmes quantiques(2006), and MINES ParisTech - École nationale supérieure des mines de Paris
Subjects: 0209 industrial biotechnology, Observer (quantum physics), Field (physics), Population, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, [SPI.AUTO]Engineering Sciences [physics]/Automatic, symbols.namesake, 020901 industrial engineering & automation, 0103 physical sciences, Quantum system, Statistical physics, 010306 general physics, education, Physics, Quantum Physics, education.field_of_study, Observable, parameter estimation -nonlinear observers -averaging, Moment (mathematics), Nonlinear systems -quantum systems, Dipole, symbols, Quantum Physics (quant-ph), Hamiltonian (quantum mechanics)
Abstract: An observer-based Hamiltonian identification algorithm for quantum systems has been proposed recently by Bonnabel et al. The later paper provided a method to estimate the dipole moment matrix of a quantum system requiring the measurement of the populations on all states, which could be experimentally difficult to achieve. We propose here an extension to a 3-level quantum system, having access to the population of the ground state only. By more adapted choice of the control field, we will show that a continuous measurement of this observable, alone, is enough to identify the field coupling parameters (dipole moment)., submitted
Published: 2009
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46. Schrödinger’s cat could help cut quantum errors.

Author: Padavic-Callaghan, Karmela
Subjects: QUANTUM computing, QUANTUM computers, QUBITS
Abstract: Researchers have developed a quantum bit, or qubit, inspired by Schrödinger's cat that can operate without errors for an extended period of time. Quantum computers have the potential to solve problems that traditional computers cannot, but they often make errors during computation. The qubit created by the researchers, known as a "cat qubit," can function for 10 seconds without errors, which is significantly longer than previous experiments. While this development is promising, there are still other types of errors that need to be addressed. [Extracted from the article]
Published: 2024
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47. Convergence of Bipartite Open Quantum Systems Stabilized by Reservoir Engineering

Author: Robin, Rémi, Rouchon, Pierre, and Sellem, Lev-Arcady
Published: 2024
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48. Cat-qubits for quantum computation

Author: Mirrahimi, Mazyar
Published: 2016
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49. Quantum Computing: Predictions and Challenges.

Author: Kulik, S. P.
Abstract: A brief overview of the state of the art in the field of quantum computing is presented and the main problems in the construction of full-scale quantum computers, as well as ways to solve them, are discussed. [ABSTRACT FROM AUTHOR]
Published: 2023
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50. Perspective on superconducting qubit quantum computing.

Author: Ezratty, Olivier
Subjects: QUANTUM computing, QUANTUM computers, QUANTUM theory, QUBITS
Abstract: This perspective describes the history, scientific and technology developments of superconducting qubit-based quantum computers, which are currently dominant, particularly with industry vendors. Adopting an engineering viewpoint, it showcases the great diversity of technology options, explains how superconducting qubit chipsets are manufactured, describes some challenges with how qubits are driven by classical electronics, how to improve their fidelities and how their energetic footprint can be optimized. We also briefly describe the current status of so-called NISQ (noisy intermediate scale quantum) computers and the resource estimations to run their potential use cases, particularly for running quantum many-body physics simulations. [ABSTRACT FROM AUTHOR]
Published: 2023
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