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8 results on '"coherent transfer"'

1. Coherent anharmonicity transfer from matter to light in the THz regime

Author

Mauricio Arias, Johan F Triana, Aldo Delgado, and Felipe Herrera

Subjects
quantum wells, non-linear phase, light–matter interaction, coherent transfer, cavity-QED, Science, Physics, QC1-999
Abstract

Optical nonlinearities are fundamental in several types of optical information processing protocols. However, the high laser intensities needed for implementing phase nonlinearities using conventional optical materials represent a challenge for nonlinear optics in the few-photon regime. We introduce an infrared cavity quantum electrodynamics (QED) approach for imprinting nonlinear phase shifts on individual THz pulses in reflection setups, conditional on the input power. Power-dependent phase shifts on the order of $ 0.1\, \pi$ can be achieved with femtosecond pulses of only a few µ W input power. The proposed scheme involves a small number of intersubband quantum well transition dipoles evanescently coupled to the near field of an infrared resonator. The field evolution is nonlinear due to the dynamical transfer of spectral anharmonicity from material dipoles to the infrared vacuum, through an effective dipolar chirping mechanism that transiently detunes the quantum well transitions from the vacuum field, leading to photon blockade. We develop analytical theory that describes the dependence of the imprinted nonlinear phase shift on relevant physical parameters. For a pair of quantum well dipoles, the phase control scheme is shown to be robust with respect to inhomogeneities in the dipole transition frequencies and relaxation rates. Numerical results based on the Lindblad quantum master equation validate the theory in the regime where the material dipoles are populated up to the second excitation manifold. In contrast with conventional QED schemes for phase control that require strong light–matter interaction, the proposed phase nonlinearity works best in weak coupling, increasing the prospects for its experimental realization using current nanophotonic technology.

Published
2024
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2. Tailoring the Energy Manifold of Quasi‐Two‐Dimensional Perovskites for Efficient Carrier Extraction.

Author

Ramesh, Sankaran, Giovanni, David, Righetto, Marcello, Ye, Senyun, Fresch, Elisa, Wang, Yue, Collini, Elisabetta, Mathews, Nripan, and Sum, Tze Chien

Subjects
*PEROVSKITE, *SOLAR cell efficiency, *ENERGY dissipation, *ENERGY harvesting, *QUANTUM wells
Abstract

Harvesting the excess energy from absorbed above bandgap photons is a promising approach to overcome the detailed balance limit for higher solar cell efficiencies. However, this remains very challenging for 2D layered halide perovskites as the fast excess energy loss competes effectively with charge extraction. Herein, the authors engineer the energy cascade manifold of quantum well (QW) states in quasi‐2D Ruddlesden–Popper perovskites by facile tuning of the organic spacer to decelerate the energy loss. The resulting excess energy loss rate is up to two orders slower compared to 3D perovskites, thus enabling efficient carrier extraction. 2D electronic spectroscopy reveals further insights into the structural and energetic disorder of these layered systems. Importantly, a judicious choice of the organic spacer holds the key to tailoring the coherent coupling between QWs that strongly influences the competition between the energy cascade and charge extraction. [ABSTRACT FROM AUTHOR]

Published
2022
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3. Coherent transfer between electron and nuclear spin qubits and their decoherence properties

Author

Brown, Richard Matthew, Morton, John J. L., Briggs, G. Andrew D., and Ardavan, Arzhang

Subjects
004.1, Quantum information processing, Nanostructures, Condensed Matter Physics, Spectroscopy and molecular structure, NMR spectroscopy, Nanomaterials, Physical & theoretical chemistry, Semiconductors, Silicon, quantum memory, coherent transfer, electron spin resonance, electron paramagnetic resonance, quantum information processing, quantum computing, fullerene, Sc@C82, La@C82, metallofullerene, P, Si, phosphorous doped silicon, decoherence, relaxation, qubit, nuclear spin, electron spin, entanglement, microwave, radiofrequency, pulsed, laser
Abstract

Conventional computing faces a huge technical challenge as traditional transistors will soon reach their size limitations. This will halt progress in reaching faster processing speeds and to overcome this problem, require an entirely new approach. Quantum computing (QC) is a natural solution offering a route to miniaturisation by, for example, storing information in electron or nuclear spin states, whilst harnessing the power of quantum physics to perform certain calculations exponentially faster than its classical counterpart. However, QCs face many difficulties, such as, protecting the quantum-bit (qubit) from the environment and its irreversible loss through the process of decoherence. Hybrid systems provide a route to harnessing the benefits of multiple degrees of freedom through the coherent transfer of quantum information between them. In this thesis I show coherent qubit transfer between electron and nuclear spin states in a 15N@C60 molecular system (comprising a nitrogen atom encapsulated in a carbon cage) and a solid state system, using phosphorous donors in silicon (Si:P). The propagation uses a series of resonant mi- crowave and radiofrequency pulses and is shown with a two-way fidelity of around 90% for an arbitrary qubit state. The transfer allows quantum information to be held in the nuclear spin for up to 3 orders of magnitude longer than in the electron spin, producing a 15N@C60 and Si:P ‘quantum memory’ of up to 130 ms and 1.75 s, respectively. I show electron and nuclear spin relaxation (T1), in both systems, is dominated by a two-phonon process resonant with an excited state, with a constant electron/nuclear T1 ratio. The thesis further investigates the decoherence and relaxation properties of metal atoms encapsulated in a carbon cage, termed metallofullerenes, discovering that exceptionally long electron spin decoherence times are possible, such that these can be considered a viable QC candidate.

Published
2012

4. Tailoring the Energy Manifold of Quasi-Two-Dimensional Perovskites for Efficient Carrier Extraction

Author

Sankaran Ramesh, David Giovanni, Marcello Righetto, Senyun Ye, Elisa Fresch, Yue Wang, Elisabetta Collini, Nripan Mathews, Tze Chien Sum, Interdisciplinary Graduate School (IGS), School of Physical and Mathematical Sciences, School of Materials Science and Engineering, and Energy Research Institute @ NTU (ERI@N)

Subjects
Ruddlesden-Popper perovskites, Renewable Energy, Sustainability and the Environment, coherent transfer, Ruddlesden-Popper Perovskite, spacer cations, General Materials Science, carrier extraction, energy cascades, Physics::Optics and light [Science], Materials::Energy materials [Engineering], Energy Cascade
Abstract

Harvesting the excess energy from absorbed above bandgap photons is a promising approach to overcome the detailed balance limit for higher solar cell efficiencies. However, this remains very challenging for 2D layered halide perovskites as the fast excess energy loss competes effectively with charge extraction. Herein, the authors engineer the energy cascade manifold of quantum well (QW) states in quasi-2D Ruddlesden–Popper perovskites by facile tuning of the organic spacer to decelerate the energy loss. The resulting excess energy loss rate is up to two orders slower compared to 3D perovskites, thus enabling efficient carrier extraction. 2D electronic spectroscopy reveals further insights into the structural and energetic disorder of these layered systems. Importantly, a judicious choice of the organic spacer holds the key to tailoring the coherent coupling between QWs that strongly influences the competition between the energy cascade and charge extraction. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version The authors acknowledge Dr. Teddy Salim from the Facility for Analysis Characterization Testing and Simulation (FACTS), School of Material Science and Engineering, Nanyang Technological University, for the UPS measurement. This research/project was supported by the Ministry of Education under its AcRF Tier 2 grants (MOE2019-T2-1-006, MOE2019-T2-1-097, and MOE-T2EP50120-0004); and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI-2018-04). E.C. acknowledges the “CQ-TECH” STARS Grant 2019 (2019-UNPD0Z9-0166571). E.F. acknowledges a Ph.D. fellowship from the Department of Excellence program “NExuS.

Published
2022

5. Tunable and robust long-range coherent interactions between quantum emitters mediated by Weyl bound states

Author

Alejandro González-Tudela, Jorge Bravo-Abad, Iñaki García-Elcano, UAM. Departamento de Física Teórica de la Materia Condensada, Ministerio de Ciencia, Innovación y Universidades (España), and Consejo Superior de Investigaciones Científicas (España)

Subjects
Coherent Transfer, Coherent Interaction, FOS: Physical sciences, General Physics and Astronomy, Quantum simulator, Quantum entanglement, Quantum Simulations, Interacting System, Quantum mechanics, Bound state, Quantum information, Wave function, Quantum, Physics, Quantum Physics, Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), Física, Dissipation, Important Features, Simulation Technologies, Spatial Confinement, Quantum Information, Quantum Physics (quant-ph), Physics - Optics, Optics (physics.optics), Coherence (physics)
Abstract

6 pags., 4 figs., Long-range coherent interactions between quantum emitters are instrumental for quantum information and simulation technologies, but they are generally difficult to isolate from dissipation. Here, we show how such interactions can be obtained in photonic Weyl environments due to the emergence of an exotic bound state whose wave function displays power-law spatial confinement. Using an exact formalism, we show how this bound state can mediate coherent transfer of excitations between emitters, with virtually no dissipation and with a transfer rate that follows the same scaling with distance as the bound state wave function. In addition, we show that the topological nature of Weyl points translates into two important features of the Weyl bound state, and, consequently, of the interactions it mediates: first, its range can be tuned without losing the power-law confinement, and, second, they are robust under energy disorder of the bath. To our knowledge, this is the first proposal of a photonic setup that combines simultaneously coherence, tunability, long range, and robustness to disorder. These findings could ultimately pave the way for the design of more robust long-distance entanglement protocols or quantum simulation implementations for studying long-range interacting systems., We acknowledge financial support from the Spanish MCIU under Grant No. RTI2018-098452-B-I00 (MCIU/ AEI/FEDER, UE) and the “María de Maeztu” programme for Units of Excellence in R&D (MDM-2014-0377 and CEX2018-000805-M). A. G. T. acknowledges support from CSIC Research Platform on Quantum Technologies PTI-001 and from Spanish project PGC2018-094792-B100 (MCIU/AEI/FEDER, EU). I. G. E. acknowledges financial support from the Ministry of Science and`Innovation of Spain (FPU Grant No. AP-2018-02748)

Published
2020

6. Coherence selection in double CP MAS NMR spectroscopy

Author

Yang, Jen-Hsien, Chou, Fang-Chieh, and Tzou, Der-Lii M.

Subjects
*SPECTRUM analysis, *GLUCOSAMINE, *OCCULTISM, *NUCLEAR magnetic resonance spectroscopy
Abstract

Abstract: Applications of double cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy, via 1H/15N and then 15N/13C coherence transfers, for 13C coherence selection are demonstrated on a 15N/13C-labeled N-acetyl-glucosamine (GlcNAc) compound. The 15N/13C coherence transfer is very sensitive to the settings of the experimental parameters. To resolve explicitly these parameter dependences, we have systematically monitored the 13C{15N/1H} signal as a function of the rf field strength and the MAS frequency. The data reveal that the zero-quantum coherence transfer, with which the 13C effective rf field is larger than that of the 15N by the spinning frequency, would give better signal sensitivity. We demonstrate in one- and two-dimensional double CP experiments that spectral editing can be achieved by tailoring the experimental parameters, such as the rf field strengths and/or the MAS frequency. [Copyright &y& Elsevier]

Published
2008
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7. Coherent Creation of Single Molecules from Single Atoms

Author

Yu, Yichao

Subjects
Coherent Transfer, Molecule Assembly, Optical Tweezer, Photoassociation, Raman Sideband Cooling, Ultracold Molecules, Molecular physics, Atomic physics, Quantum physics
Abstract

Molecules, with their rich spectrum of internal states as well as strong and tunable dipolar interactions, are promising candidates for a broad range of experiments including quantum information, quantum chemistry, precision measurement and probing physics beyond the Standard Model, and quantum simulation of interacting many-body systems. At the same time, the complexity that made them attractive also poses a significant challenge to achieve a high level of quantum control that is required in many of their potential applications. Multiple approaches are being pursued for full quantum control of molecules including association of atomic gases and direct cooling of molecules, yet it remains challenging to control molecules at single particle level due to the difficulty in tuning the atom-atom interaction and laser cooling of molecules. In this thesis, we achieved full control on a single weakly bound ground state molecule created by coherent optical association from single atoms. We first discuss the trapping and imaging of the atoms in the optical tweezer and the cooling into a single quantum state in order to achieve the quantum control of atoms. Combining this control with the resolution and flexibility of tweezers. we developed a versatile platform to study interactions between single atoms and properties of single molecules, using precise optical spectroscopy on pairs of atoms in the tweezer. Based on these studies, we proposed a promising pathway for coherent all-optical creation of molecules and experimentally demonstrated full control on the molecule including all degrees of freedom.

Published
2021

8. Softening of spin resonance at low temperature in p-doped Cd1-xMnxTe quantum wells

Author

Scalbert, Denis, Teppe, Frederic, Vladimirova, Maria, Tatarenko, Serge, Cibert, J., Nawrocki, M., Groupe d'étude des semiconducteurs (GES), and Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS)

Subjects
FERROMAGNETISM, COHERENT TRANSFER, EXCITONS, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], SHIFT, Condensed Matter::Strongly Correlated Electrons, MAGNETIC SEMICONDUCTORS, 2-DIMENSIONAL HOLE GAS, PRECESSION
Abstract

International audience; Time-domain spin resonances in p-doped CdMnTe quantum wells have been studied via time-resolved magneto-optical Kerr rotation. The resonances related to quantum well electrons Mn and electrons excited in the substrate are identified. An additional spin resonance which shows an unusual temperature dependence is detected in one of the samples. The corresponding frequency tends to zero when approaching the Curie temperature. This "soft" spin precession mode has been studied as a function of magnetic field, temperature, magnetic field orientation, and optical excitation density. Its origin is discussed in the framework of the existing collective spin excitation model.

Published
2004
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