150 results on '"Linke, N"'
Search Results
2. Many Body Thermodynamics on Quantum Computers via Partition Function Zeros
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Francis, Akhil, Zhu, D., Alderete, C. Huerta, Johri, Sonika, Xiao, Xiao, Freericks, J. K., Monroe, C., Linke, N. M., and Kemper, A. F.
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Quantum Physics ,Condensed Matter - Statistical Mechanics ,Condensed Matter - Strongly Correlated Electrons - Abstract
Interacting quantum systems illustrate complex phenomena including phase transitions to novel ordered phases. The universal nature of critical phenomena reduces their description to determining only the transition temperature and the critical exponents. Numerically calculating these results for systems in new universality classes is complicated due to critical slowing down, requiring increasing resources near the critical point. An alternative approach analytically continues the calculation onto the complex plane and determines the partition function via its zeros. Here we show how to robustly perform this analysis on noisy intermediate scale trapped ion quantum computers in a scalable manner, using the XXZ model as a prototype. We illustrate the transition from XY-like behavior to Ising-like behavior as a function of the anisotropy. While quantum computers cannot yet scale to the thermodynamic limit, our work provides a pathway to do so as hardware improves, allowing the determination of critical phenomena for systems that cannot be solved otherwise., Comment: 6 pages, 5 figures, Supplementary material with 6 pages and 5 figures
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- 2020
3. Probing many-body localization on a noisy quantum computer
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Zhu, D., Johri, S., Nguyen, N. H., Alderete, C. Huerta, Landsman, K. A., Linke, N. M., Monroe, C., and Matsuura, A. Y.
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Quantum Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
A disordered system of interacting particles exhibits localized behavior when the disorder is large compared to the interaction strength. Studying this phenomenon on a quantum computer without error correction is challenging because even weak coupling to a thermal environment destroys most signatures of localization. Fortunately, spectral functions of local operators are known to contain features that can survive the presence of noise. In these spectra, discrete peaks and a soft gap at low frequencies compared to the thermal phase indicate localization. Here, we present the computation of spectral functions on a trapped-ion quantum computer for a one-dimensional Heisenberg model with disorder. Further, we design an error-mitigation technique which is effective at removing the noise from the measurement allowing clear signatures of localization to emerge as the disorder increases. Thus, we show that spectral functions can serve as a robust and scalable diagnostic of many-body localization on the current generation of quantum computers.
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- 2020
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4. Programmable Quantum Simulations of Spin Systems with Trapped Ions
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Monroe, C., Campbell, W. C., Duan, L. -M., Gong, Z. -X., Gorshkov, A. V., Hess, P., Islam, R., Kim, K., Linke, N., Pagano, G., Richerme, P., Senko, C., and Yao, N. Y.
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Quantum Physics ,Condensed Matter - Materials Science - Abstract
Laser-cooled and trapped atomic ions form an ideal standard for the simulation of interacting quantum spin models. Effective spins are represented by appropriate internal energy levels within each ion, and the spins can be measured with near-perfect efficiency using state-dependent fluorescence techniques. By applying optical fields that exert optical dipole forces on the ions, their Coulomb interaction can be modulated to produce long-range and tunable spin-spin interactions that can be reconfigured by shaping the spectrum and pattern of the laser fields, in a prototypical example of a quantum simulator. Here we review the theoretical mapping of atomic ions to interacting spin systems, the preparation of complex equilibrium states, the study of dynamical processes in these many-body interacting quantum systems, and the use of this platform for optimization and other tasks. The use of such quantum simulators for studying spin models may inform our understanding of exotic quantum materials and shed light on the behavior of interacting quantum systems that cannot be modeled with conventional computers.
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- 2019
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5. Dynamical mean field theory algorithm and experiment on quantum computers
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Rungger, I., Fitzpatrick, N., Chen, H., Alderete, C. H., Apel, H., Cowtan, A., Patterson, A., Ramo, D. Munoz, Zhu, Y., Nguyen, N. H., Grant, E., Chretien, S., Wossnig, L., Linke, N. M., and Duncan, R.
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Quantum Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
The developments of quantum computing algorithms and experiments for atomic scale simulations have largely focused on quantum chemistry for molecules, while their application in condensed matter systems is scarcely explored. Here we present a quantum algorithm to perform dynamical mean field theory (DMFT) calculations for condensed matter systems on currently available quantum computers, and demonstrate it on two quantum hardware platforms. DMFT is required to properly describe the large class of materials with strongly correlated electrons. The computationally challenging part arises from solving the effective problem of an interacting impurity coupled to a bath, which scales exponentially with system size on conventional computers. An exponential speedup is expected on quantum computers, but the algorithms proposed so far are based on real time evolution of the wavefunction, which requires high-depth circuits and hence very low noise levels in the quantum hardware. Here we propose an alternative approach, which uses the variational quantum eigensolver (VQE) method for ground and excited states to obtain the needed quantities as part of an exact diagonalization impurity solver. We present the algorithm for a two site DMFT system, which we benchmark using simulations on conventional computers as well as experiments on superconducting and trapped ion qubits, demonstrating that this method is suitable for running DMFT calculations on currently available quantum hardware.
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- 2019
6. Generation of Thermofield Double States and Critical Ground States with a Quantum Computer
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Zhu, D., Johri, S., Linke, N. M., Landsman, K. A., Nguyen, N. H., Alderete, C. H., Matsuura, A. Y., Hsieh, T. H., and Monroe, C.
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Quantum Physics ,Condensed Matter - Strongly Correlated Electrons ,High Energy Physics - Theory - Abstract
Finite-temperature phases of many-body quantum systems are fundamental to phenomena ranging from condensed-matter physics to cosmology, yet they are generally difficult to simulate. Using an ion trap quantum computer and protocols motivated by the Quantum Approximate Optimization Algorithm (QAOA), we generate nontrivial thermal quantum states of the transverse-field Ising model (TFIM) by preparing thermofield double states at a variety of temperatures. We also prepare the critical state of the TFIM at zero temperature using quantum-classical hybrid optimization. The entanglement structure of thermofield double and critical states plays a key role in the study of black holes, and our work simulates such nontrivial structures on a quantum computer. Moreover, we find that the variational quantum circuits exhibit noise thresholds above which the lowest depth QAOA circuits provide the best results.
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- 2019
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7. Training of Quantum Circuits on a Hybrid Quantum Computer
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Zhu, D., Linke, N. M., Benedetti, M., Landsman, K. A., Nguyen, N. H., Alderete, C. H., Perdomo-Ortiz, A., Korda, N., Garfoot, A., Brecque, C., Egan, L., Perdomo, O., and Monroe, C.
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Quantum Physics - Abstract
Generative modeling is a flavor of machine learning with applications ranging from computer vision to chemical design. It is expected to be one of the techniques most suited to take advantage of the additional resources provided by near-term quantum computers. We implement a data-driven quantum circuit training algorithm on the canonical Bars-and-Stripes data set using a quantum-classical hybrid machine. The training proceeds by running parameterized circuits on a trapped ion quantum computer, and feeding the results to a classical optimizer. We apply two separate strategies, Particle Swarm and Bayesian optimization to this task. We show that the convergence of the quantum circuit to the target distribution depends critically on both the quantum hardware and classical optimization strategy. Our study represents the first successful training of a high-dimensional universal quantum circuit, and highlights the promise and challenges associated with hybrid learning schemes., Comment: 14 pages, 4 figures
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- 2018
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8. Parallel Entangling Operations on a Universal Ion Trap Quantum Computer
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Figgatt, C., Ostrander, A., Linke, N. M., Landsman, K. A., Zhu, D., Maslov, D., and Monroe, C.
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Quantum Physics ,Computer Science - Emerging Technologies - Abstract
The circuit model of a quantum computer consists of sequences of gate operations between quantum bits (qubits), drawn from a universal family of discrete operations. The ability to execute parallel entangling quantum gates offers clear efficiency gains in numerous quantum circuits as well as for entire algorithms such as Shor's factoring algorithm and quantum simulations. In cases such as full adders and multiple-control Toffoli gates, parallelism can provide an exponential improvement in overall execution time. More importantly, quantum gate parallelism is essential for the practical fault-tolerant error correction of qubits that suffer from idle errors. The implementation of parallel quantum gates is complicated by potential crosstalk, especially between qubits fully connected by a common-mode bus, such as in Coulomb-coupled trapped atomic ions or cavity-coupled superconducting transmons. Here, we present the first experimental results for parallel 2-qubit entangling gates in an array of fully-connected trapped ion qubits. We demonstrate an application of this capability by performing a 1-bit full addition operation on a quantum computer using a depth-4 quantum circuit. These results exploit the power of highly connected qubit systems through classical control techniques, and provide an advance toward speeding up quantum circuits and achieving fault tolerance with trapped ion quantum computers.
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- 2018
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9. Observation of Hopping and Blockade of Bosons in a Trapped Ion Spin Chain
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Debnath, S., Linke, N. M., Wang, S. -T., Figgatt, C., Landsman, K. A., Duan, L. -M., and Monroe, C.
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Quantum Physics - Abstract
The local phonon modes in a Coulomb crystal of trapped ions can represent a Hubbard system of coupled bosons. We selectively prepare single excitations at each site and observe free hopping of a boson between sites, mediated by the long-range Coulomb interaction between ions. We then implement phonon blockades on targeted sites by driving a Jaynes-Cummings interaction on individually addressed ions to couple their internal spin to the local phonon mode. The resulting dressed states have energy splittings that can be tuned to suppress phonon hopping into the site. This new experimental approach opens up the possibility of realizing large-scale Hubbard systems from the bottom up with tunable interactions at the single-site level., Comment: 8 pages, 5 figures, 1 table. Supplementary materials included
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- 2017
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10. Cross-platform comparison of arbitrary quantum states
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Zhu, D., Cian, Z. P., Noel, C., Risinger, A., Biswas, D., Egan, L., Zhu, Y., Green, A. M., Alderete, C. Huerta, Nguyen, N. H., Wang, Q., Maksymov, A., Nam, Y., Cetina, M., Linke, N. M., Hafezi, M., and Monroe, C.
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- 2022
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11. Complete 3-Qubit Grover Search on a Programmable Quantum Computer
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Figgatt, C., Maslov, D., Landsman, K. A., Linke, N. M., Debnath, S., and Monroe, C.
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Quantum Physics ,Computer Science - Emerging Technologies - Abstract
Searching large databases is an important problem with broad applications. The Grover search algorithm provides a powerful method for quantum computers to perform searches with a quadratic speedup in the number of required database queries over classical computers. It is an optimal search algorithm for a quantum computer, and has further applications as a subroutine for other quantum algorithms. Searches with two qubits have been demonstrated on a variety of platforms and proposed for others, but larger search spaces have only been demonstrated on a non-scalable NMR system. Here, we report results for a complete three-qubit Grover search algorithm using the scalable quantum computing technology of trapped atomic ions, with better-than-classical performance. The algorithm is performed for all 8 possible single-result oracles and all 28 possible two-result oracles. Two methods of state marking are used for the oracles: a phase-flip method employed by other experimental demonstrations, and a Boolean method requiring an ancilla qubit that is directly equivalent to the state-marking scheme required to perform a classical search. All quantum solutions are shown to outperform their classical counterparts. We also report the first implementation of a Toffoli-4 gate, which is used along with Toffoli-3 gates to construct the algorithms; these gates have process fidelities of 70.5% and 89.6%, respectively., Comment: 11 pages, 10 figures, 2 tables
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- 2017
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12. Experimental Comparison of Two Quantum Computing Architectures
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Linke, N. M., Maslov, D., Roetteler, M., Debnath, S., Figgatt, C., Landsman, K. A., Wright, K., and Monroe, C.
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Quantum Physics ,Computer Science - Emerging Technologies - Abstract
We run a selection of algorithms on two state-of-the-art 5-qubit quantum computers that are based on different technology platforms. One is a publicly accessible superconducting transmon device with limited connectivity, and the other is a fully connected trapped-ion system. Even though the two systems have different native quantum interactions, both can be programmed in a way that is blind to the underlying hardware, thus allowing the first comparison of identical quantum algorithms between different physical systems. We show that quantum algorithms and circuits that employ more connectivity clearly benefit from a better connected system of qubits. While the quantum systems here are not yet large enough to eclipse classical computers, this experiment exposes critical factors of scaling quantum computers, such as qubit connectivity and gate expressivity. In addition, the results suggest that co-designing particular quantum applications with the hardware itself will be paramount in successfully using quantum computers in the future.
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- 2017
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13. Fault-tolerant quantum error detection
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Linke, N. M., Gutierrez, M., Landsman, K. A., Figgatt, C., Debnath, S., Brown, K. R., and Monroe, C.
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Quantum Physics - Abstract
Quantum computers will eventually reach a size at which quantum error correction becomes imperative. Quantum information can be protected from qubit imperfections and flawed control operations by encoding a single logical qubit in multiple physical qubits. This redundancy allows the extraction of error syndromes and the subsequent detection or correction of errors without destroying the logical state itself through direct measurement. Here we show the encoding and syndrome measurement of a fault-tolerant logical qubit via an error detection protocol on four physical qubits, represented by trapped atomic ions. This demonstrates for the first time the robustness of a fault-tolerant qubit to imperfections in the very operations used to encode it. The advantage persists in the face of large added error rates and experimental calibration errors., Comment: 17 pages, 4 figures, 1 table, 5 physical qubits, 2 logical qubits, 1 of which is fault-tolerant
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- 2016
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14. Generation of thermofield double states and critical ground states with a quantum computer
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Zhu, D., Johri, S., Linke, N. M., Landsman, K. A., Alderete, C. Huerta, Nguyen, N. H., Matsuurad, A. Y., Hsieh, T. H., and Monroe, C.
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- 2020
15. Demonstration of a small programmable quantum computer with atomic qubits
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Debnath, S., Linke, N. M., Figgatt, C., Landsman, K. A., Wright, K., and Monroe, C.
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Quantum Physics - Abstract
Quantum computers can solve certain problems more efficiently than any possible conventional computer. Small quantum algorithms have been demonstrated on multiple quantum computing platforms, many specifically tailored in hardware to implement a particular algorithm or execute a limited number of computational paths. Here, we demonstrate a five-qubit trapped-ion quantum computer that can be programmed in software to implement arbitrary quantum algorithms by executing any sequence of universal quantum logic gates. We compile algorithms into a fully-connected set of gate operations that are native to the hardware and have a mean fidelity of 98 %. Reconfiguring these gate sequences provides the flexibility to implement a variety of algorithms without altering the hardware. As examples, we implement the Deutsch-Jozsa (DJ) and Bernstein-Vazirani (BV) algorithms with average success rates of 95 % and 90 %, respectively. We also perform a coherent quantum Fourier transform (QFT) on five trappedion qubits for phase estimation and period finding with average fidelities of 62 % and 84 %, respectively. This small quantum computer can be scaled to larger numbers of qubits within a single register, and can be further expanded by connecting several such modules through ion shuttling or photonic quantum channels., Comment: 10 pages, 5 figures
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- 2016
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16. High-fidelity spatial and polarization addressing of Ca-43 qubits using near-field microwave control
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Craik, D. P. L. Aude, Linke, N. M., Sepiol, M. A., Harty, T. P., Goodwin, J. F., Ballance, C. J., Stacey, D. N., Steane, A. M., Lucas, D. M., and Allcock, D. T. C.
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Quantum Physics ,Physics - Atomic Physics - Abstract
Individual addressing of qubits is essential for scalable quantum computation. Spatial addressing allows unlimited numbers of qubits to share the same frequency, whilst enabling arbitrary parallel operations. We demonstrate addressing of long-lived $^{43}\text{Ca}^+$ "atomic clock" qubits held in separate zones ($960\mu$m apart) of a microfabricated surface trap with integrated microwave electrodes. Such zones could form part of a "quantum CCD" architecture for a large-scale quantum information processor. By coherently cancelling the microwave field in one zone we measure a ratio of Rabi frequencies between addressed and non-addressed qubits of up to 1400, from which we calculate a spin-flip probability on the qubit transition of the non-addressed ion of $1.3\times 10^{-6}$. Off-resonant excitation then becomes the dominant error process, at around $5 \times 10^{-3}$. It can be prevented either by working at higher magnetic field, or by polarization control of the microwave field. We implement polarization control with error $2 \times 10^{-5}$, which would suffice to suppress off-resonant excitation to the $\sim 10^{-9}$ level if combined with spatial addressing. Such polarization control could also enable fast microwave operations., Comment: 11 pages, 4 figures
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- 2016
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17. High-fidelity quantum logic gates using trapped-ion hyperfine qubits
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Ballance, C. J., Harty, T. P., Linke, N. M., Sepiol, M. A., and Lucas, D. M.
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Quantum Physics - Abstract
We demonstrate laser-driven two-qubit and single-qubit logic gates with fidelities 99.9(1)% and 99.9934(3)% respectively, significantly above the approximately 99% minimum threshold level required for fault-tolerant quantum computation, using qubits stored in hyperfine ground states of calcium-43 ions held in a room-temperature trap. We study the speed/fidelity trade-off for the two-qubit gate, for gate times between 3.8$\mu$s and 520$\mu$s, and develop a theoretical error model which is consistent with the data and which allows us to identify the principal technical sources of infidelity., Comment: 1 trap, 2 ions, 3 nines. Detailed write-up of arXiv:1406.5473 including single-qubit gate data also
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- 2015
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18. Hybrid quantum logic and a test of Bell's inequality using two different atomic isotopes
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Ballance, C. J., Schaefer, V. M., Home, J. P., Szwer, D. J., Webster, S. C., Allcock, D. T. C., Linke, N. M., Harty, T. P., Craik, D. P. L. Aude, Stacey, D. N., Steane, A. M., and Lucas, D. M.
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Quantum Physics ,Physics - Atomic Physics - Abstract
Entanglement is one of the most fundamental properties of quantum mechanics, and is the key resource for quantum information processing. Bipartite entangled states of identical particles have been generated and studied in several experiments, and post-selected or heralded entangled states involving pairs of photons, single photons and single atoms, or different nuclei in the solid state, have also been produced. Here, we use a deterministic quantum logic gate to generate a "hybrid" entangled state of two trapped-ion qubits held in different isotopes of calcium, perform full tomography of the state produced, and make a test of Bell's inequality with non-identical atoms. We use a laser-driven two-qubit gate, whose mechanism is insensitive to the qubits' energy splittings, to produce a maximally-entangled state of one Ca-40 qubit and one Ca-43 qubit, held 3.5 microns apart in the same ion trap, with 99.8(6)% fidelity. We test the Clauser-Horne-Shimony-Holt (CHSH) version of Bell's inequality for this novel entangled state and find that it is violated by 15 standard deviations; in this test, we close the detection loophole but not the locality loophole. Mixed-species quantum logic is a powerful technique for the construction of a quantum computer based on trapped ions, as it allows protection of memory qubits while other qubits undergo logic operations, or are used as photonic interfaces to other processing units. The entangling gate mechanism used here can also be applied to qubits stored in different atomic elements; this would allow both memory and logic gate errors due to photon scattering to be reduced below the levels required for fault-tolerant quantum error correction, which is an essential pre-requisite for general-purpose quantum computing., Comment: 5 pages, 3 figures, 2 isotopes, 1 table
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- 2015
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19. High-fidelity two-qubit quantum logic gates using trapped calcium-43 ions
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Ballance, C. J., Harty, T. P., Linke, N. M., and Lucas, D. M.
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Quantum Physics ,Physics - Atomic Physics - Abstract
We study the speed/fidelity trade-off for a two-qubit phase gate implemented in $^{43}$Ca$^+$ hyperfine trapped-ion qubits. We characterize various error sources contributing to the measured fidelity, allowing us to account for errors due to single-qubit state preparation, rotation and measurement (each at the $\sim0.1\%$ level), and to identify the leading sources of error in the two-qubit entangling operation. We achieve gate fidelities ranging between $97.1(2)\%$ (for a gate time $t_g=3.8\mu$s) and $99.9(1)\%$ (for $t_g=100\mu$s), representing respectively the fastest and lowest-error two-qubit gates reported between trapped-ion qubits by nearly an order of magnitude in each case., Comment: Preliminary report; more details to be given in a future version. 1 trap, 2 ions, 3 nines
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- 2014
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20. High-fidelity preparation, gates, memory and readout of a trapped-ion quantum bit
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Harty, T. P., Allcock, D. T. C., Ballance, C. J., Guidoni, L., Janacek, H. A., Linke, N. M., Stacey, D. N., and Lucas, D. M.
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Quantum Physics - Abstract
We implement all single-qubit operations with fidelities significantly above the minimum threshold required for fault-tolerant quantum computing, using a trapped-ion qubit stored in hyperfine "atomic clock" states of $^{43}$Ca$^+$. We measure a combined qubit state preparation and single-shot readout fidelity of 99.93%, a memory coherence time of $T^*_2=50$ seconds, and an average single-qubit gate fidelity of 99.9999%. These results are achieved in a room-temperature microfabricated surface trap, without the use of magnetic field shielding or dynamic decoupling techniques to overcome technical noise., Comment: Supplementary Information included. 6 nines, 7 figures, 8 pages
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- 2014
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21. Injection locking of two frequency-doubled lasers with 3.2 GHz offset for driving Raman transitions with low photon scattering in $^{43}$Ca$^+$
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Linke, N. M., Ballance, C. J., and Lucas, D. M.
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Physics - Atomic Physics - Abstract
We describe the injection locking of two infrared (794 nm) laser diodes which are each part of a frequency-doubled laser system. An acousto-optic modulator (AOM) in the injection path gives an offset of 1.6 GHz between the lasers for driving Raman transitions between states in the hyperfine split (by 3.2 GHz) ground level of $^{43}$Ca$^+$. The offset can be disabled for use in $^{40}$Ca$^+$. We measure the relative linewidth of the frequency-doubled beams to be 42 mHz in an optical heterodyne measurement. The use of both injection locking and frequency doubling combines spectral purity with high optical power. Our scheme is applicable for providing Raman beams across other ion species and neutral atoms where coherent optical manipulation is required., Comment: 3 pages, 3 figures
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- 2013
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22. Microwave control electrodes for scalable, parallel, single-qubit operations in a surface-electrode ion trap
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Craik, D. P. L. Aude, Linke, N. M., Harty, T. P., Ballance, C. J., Lucas, D. M., Steane, A. M., and Allcock, D. T. C.
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Quantum Physics ,Physics - Atomic Physics - Abstract
We propose a surface ion trap design incorporating microwave control electrodes for near-field single-qubit control. The electrodes are arranged so as to provide arbitrary frequency, amplitude and polarization control of the microwave field in one trap zone, while a similar set of electrodes is used to null the residual microwave field in a neighbouring zone. The geometry is chosen to reduce the residual field to the 0.5% level without nulling fields; with nulling, the crosstalk may be kept close to the 0.01% level for realistic microwave amplitude and phase drift. Using standard photolithography and electroplating techniques, we have fabricated a proof-of-principle electrode array with two trapping zones. We discuss requirements for the microwave drive system and prospects for scalability to a large two-dimensional trap array., Comment: 8 pages, 6 figures
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- 2013
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23. A microfabricated ion trap with integrated microwave circuitry
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Allcock, D. T. C., Harty, T. P., Ballance, C. J., Keitch, B. C., Linke, N. M., Stacey, D. N., and Lucas, D. M.
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Physics - Atomic Physics ,Physics - Instrumentation and Detectors ,Quantum Physics - Abstract
We describe the design, fabrication and testing of a surface-electrode ion trap, which incorporates microwave waveguides, resonators and coupling elements for the manipulation of trapped ion qubits using near-field microwaves. The trap is optimised to give a large microwave field gradient to allow state-dependent manipulation of the ions' motional degrees of freedom, the key to multiqubit entanglement. The microwave field near the centre of the trap is characterised by driving hyperfine transitions in a single laser-cooled 43Ca+ ion., Comment: 4 pages, 5 figures
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- 2012
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24. Background-free detection of trapped ions
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Linke, N. M., Allcock, D. T. C., Szwer, D. J., Ballance, C. J., Harty, T. P., Janacek, H. A., Stacey, D. N., Steane, A. M., and Lucas, D. M.
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Physics - Atomic Physics ,Quantum Physics - Abstract
We demonstrate a Doppler cooling and detection scheme for ions with low-lying D levels which almost entirely suppresses scattered laser light background, while retaining a high fluorescence signal and efficient cooling. We cool a single ion with a laser on the 2S1/2 to 2P1/2 transition as usual, but repump via the 2P3/2 level. By filtering out light on the cooling transition and detecting only the fluorescence from the 2P_3/2 to 2S1/2 decays, we suppress the scattered laser light background count rate to 1 per second while maintaining a signal of 29000 per second with moderate saturation of the cooling transition. This scheme will be particularly useful for experiments where ions are trapped in close proximity to surfaces, such as the trap electrodes in microfabricated ion traps, which leads to high background scatter from the cooling beam.
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- 2011
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25. Heating rate and electrode charging measurements in a scalable, microfabricated, surface-electrode ion trap
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Allcock, D. T. C., Harty, T. P., Janacek, H. A., Linke, N. M., Ballance, C. J., Steane, A. M., Lucas, D. M., Jarecki Jr., R. L., Habermehl, S. D., Blain, M. G., Stick, D., and Moehring, D. L.
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Quantum Physics - Abstract
We characterise the performance of a surface-electrode ion "chip" trap fabricated using established semiconductor integrated circuit and micro-electro-mechanical-system (MEMS) microfabrication processes which are in principle scalable to much larger ion trap arrays, as proposed for implementing ion trap quantum information processing. We measure rf ion micromotion parallel and perpendicular to the plane of the trap electrodes, and find that on-package capacitors reduce this to <~ 10 nm in amplitude. We also measure ion trapping lifetime, charging effects due to laser light incident on the trap electrodes, and the heating rate for a single trapped ion. The performance of this trap is found to be comparable with others of the same size scale., Comment: 6 pages, 10 figures
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- 2011
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26. Implementation of a symmetric surface electrode ion trap with field compensation using a modulated Raman effect
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Allcock, D. T. C., Sherman, J. A., Stacey, D. N., Burrell, A. H., Curtis, M. J., Imreh, G., Linke, N. M., Szwer, D. J., Webster, S. C., Steane, A. M., and Lucas, D. M.
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Quantum Physics ,Physics - Atomic Physics - Abstract
We describe the fabrication and characterization of a new surface-electrode Paul ion trap designed for experiments in scalable quantum information processing with Ca+. A notable feature is a symmetric electrode pattern which allows rotation of the normal modes of ion motion, yielding efficient Doppler cooling with a single beam parallel to the planar surface. We propose and implement a technique for micromotion compensation in all directions using an infrared repumper laser beam directed into the trap plane. Finally, we employ an alternate repumping scheme that increases ion fluorescence and simplifies heating rate measurements obtained by time-resolved ion fluorescence during Doppler cooling., Comment: 9 pages, 14 figures; Rewritten section IB and added authors
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- 2009
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27. Deterministic Ultracold Ion Source targeting the Heisenberg Limit
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Schnitzler, W., Linke, N. M., Fickler, R., Meijer, J., Schmidt-Kaler, F., and Singer, K.
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Quantum Physics - Abstract
The major challenges to fabricate quantum processors and future nano solid state devices are material modification techniques with nanometre resolution and suppression of statistical fluctuations of dopants or qubit carriers. Based on a segmented ion trap with mK laser cooled ions we have realized a deterministic single ion source which could operate with a huge range of sympathetically cooled ion species, isotopes or ionic molecules. We have deterministically extracted a predetermined number of ions on demand and have measured a longitudinal velocity uncertainty of 6.3m/s and a spatial beam divergence of 0.6 mrad. We show in numerical simulations that if the ions are cooled to the motional ground state (Heisenberg limit) nanometre spatial resolution can be achieved., Comment: 4 pages 4 figures. to be published in prl
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- 2009
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28. Verified quantum information scrambling
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Landsman, K. A., Figgatt, C., Schuster, T., Linke, N. M., Yoshida, B., Yao, N. Y., and Monroe, C.
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Quantum mechanics -- Research ,Physics research ,Integrated circuits ,Atoms ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
Quantum scrambling is the dispersal of local information into many-body quantum entanglements and correlations distributed throughout an entire system. This concept accompanies the dynamics of thermalization in closed quantum systems, and has recently emerged as a powerful tool for characterizing chaos in black holes.sup.1-4. However, the direct experimental measurement of quantum scrambling is difficult, owing to the exponential complexity of ergodic many-body entangled states. One way to characterize quantum scrambling is to measure an out-of-time-ordered correlation function (OTOC); however, because scrambling leads to their decay, OTOCs do not generally discriminate between quantum scrambling and ordinary decoherence. Here we implement a quantum circuit that provides a positive test for the scrambling features of a given unitary process.sup.5,6. This approach conditionally teleports a quantum state through the circuit, providing an unambiguous test for whether scrambling has occurred, while simultaneously measuring an OTOC. We engineer quantum scrambling processes through a tunable three-qubit unitary operation as part of a seven-qubit circuit on an ion trap quantum computer. Measured teleportation fidelities are typically about 80 per cent, and enable us to experimentally bound the scrambling-induced decay of the corresponding OTOC measurement. A quantum circuit in an ion-trap quantum computer provides a positive test for the scrambling features of a given unitary process., Author(s): K. A. Landsman [sup.1] , C. Figgatt [sup.1] , T. Schuster [sup.2] , N. M. Linke [sup.1] , B. Yoshida [sup.3] , N. Y. Yao [sup.2] [sup.4] , C. [...]
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- 2019
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29. Parallel entangling operations on a universal ion-trap quantum computer
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Figgatt, C., Ostrander, A., Linke, N. M., Landsman, K. A., Zhu, D., Maslov, D., and Monroe, C.
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- 2019
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30. Comparison of 6-month outcomes of sepsis versus non-sepsis critically ill patients receiving mechanical ventilation
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Hodgson, CL, Higgins, AM, Bailey, M, Barrett, J, Bellomo, R, Cooper, DJ, Gabbe, BJ, Iwashyna, T, Linke, N, Myles, PS, Paton, M, Philpot, S, Shulman, M, Young, M, Serpa Neto, A, Hodgson, CL, Higgins, AM, Bailey, M, Barrett, J, Bellomo, R, Cooper, DJ, Gabbe, BJ, Iwashyna, T, Linke, N, Myles, PS, Paton, M, Philpot, S, Shulman, M, Young, M, and Serpa Neto, A
- Abstract
BACKGROUND: Data on long-term outcomes after sepsis-associated critical illness have mostly come from small cohort studies, with no information about the incidence of new disability. We investigated whether sepsis-associated critical illness was independently associated with new disability at 6 months after ICU admission compared with other types of critical illness. METHODS: We conducted a secondary analysis of a multicenter, prospective cohort study in six metropolitan intensive care units in Australia. Adult patients were eligible if they had been admitted to the ICU and received more than 24 h of mechanical ventilation. There was no intervention. RESULTS: The primary outcome was new disability measured with the WHO Disability Assessment Schedule 2.0 (WHODAS) 12 level score compared between baseline and 6 months. Between enrollment and follow-up at 6 months, 222/888 (25%) patients died, 100 (35.5%) with sepsis and 122 (20.1%) without sepsis (P < 0.001). Among survivors, there was no difference for the incidence of new disability at 6 months with or without sepsis, 42/106 (39.6%) and 106/300 (35.3%) (RD, 0.00 (- 10.29 to 10.40), P = 0.995), respectively. In addition, there was no difference in the severity of disability, health-related quality of life, anxiety and depression, post-traumatic stress, return to work, financial distress or cognitive function. CONCLUSIONS: Compared to mechanically ventilated patients of similar acuity and length of stay without sepsis, patients with sepsis admitted to ICU have an increased risk of death, but survivors have a similar risk of new disability at 6 months. Trial registration NCT03226912, registered July 24, 2017.
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- 2022
31. Microwave control electrodes for scalable, parallel, single-qubit operations in a surface-electrode ion trap
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Aude Craik, D. P. L., Linke, N. M., Harty, T. P., Ballance, C. J., Lucas, D. M., Steane, A. M., and Allcock, D. T. C.
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- 2014
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32. Predictors of death and new disability after critical illness: a multicentre prospective cohort study.
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Higgins A.M., Neto A.S., Bailey M., Barrett J., Bellomo R., Cooper D.J., Gabbe B.J., Linke N., Myles P.S., Paton M., Philpot S., Shulman M., Young M., Hodgson C.L., Higgins A.M., Neto A.S., Bailey M., Barrett J., Bellomo R., Cooper D.J., Gabbe B.J., Linke N., Myles P.S., Paton M., Philpot S., Shulman M., Young M., and Hodgson C.L.
- Abstract
Purpose: This study aimed to determine the prevalence and predictors of death or new disability following critical illness. Method(s): Prospective, multicentre cohort study conducted in six metropolitan intensive care units (ICU). Participants were adults admitted to the ICU who received more than 24 h of mechanical ventilation. The primary outcome was death or new disability at 6 months, with new disability defined by a 10% increase in the WHODAS 2.0. Result(s): Of 628 patients with the primary outcome available (median age of 62 [49-71] years, 379 [61.0%] had a medical admission and 370 (58.9%) died or developed new disability by 6 months. Independent predictors of death or new disability included age [OR 1.02 (1.01-1.03), P = 0.001], higher severity of illness (APACHE III) [OR 1.02 (1.01-1.03), P < 0.001] and admission diagnosis. Compared to patients with a surgical admission diagnosis, patients with a cardiac arrest [OR (95% CI) 4.06 (1.89-8.68), P < 0.001], sepsis [OR (95% CI) 2.43 (1.32-4.47), P = 0.004], or trauma [OR (95% CI) 6.24 (3.07-12.71), P < 0.001] diagnosis had higher odds of death or new disability, while patients with a lung transplant [OR (95% CI) 0.21 (0.07-0.58), P = 0.003] diagnosis had lower odds. A model including these three variables had good calibration (Brier score 0.20) and acceptable discriminative power with an area under the receiver operating characteristic curve of 0.76 (95% CI 0.72-0.80). Conclusion(s): Less than half of all patients mechanically ventilated for more than 24 h were alive and free of new disability at 6 months after admission to ICU. A model including age, illness severity and admission diagnosis has acceptable discriminative ability to predict death or new disability at 6 months.Copyright © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.
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- 2021
33. Background-free detection of trapped ions
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Linke, N. M., Allcock, D. T. C., Szwer, D. J., Ballance, C. J., Harty, T. P., Janacek, H. A., Stacey, D. N., Steane, A. M., and Lucas, D. M.
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- 2012
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34. Heating rate and electrode charging measurements in a scalable, microfabricated, surface-electrode ion trap
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Allcock, D. T. C., Harty, T. P., Janacek, H. A., Linke, N. M., Ballance, C. J., Steane, A. M., Lucas, D. M., Jarecki, Jr., R. L., Habermehl, S. D., Blain, M. G., Stick, D., and Moehring, D. L.
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- 2012
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35. Programmable quantum simulations of spin systems with trapped ions
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Monroe, C., primary, Campbell, W. C., additional, Duan, L.-M., additional, Gong, Z.-X., additional, Gorshkov, A. V., additional, Hess, P. W., additional, Islam, R., additional, Kim, K., additional, Linke, N. M., additional, Pagano, G., additional, Richerme, P., additional, Senko, C., additional, and Yao, N. Y., additional
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- 2021
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36. Probing many-body localization on a noisy quantum computer
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Zhu, D., primary, Johri, S., additional, Nguyen, N. H., additional, Alderete, C. Huerta, additional, Landsman, K. A., additional, Linke, N. M., additional, Monroe, C., additional, and Matsuura, A. Y., additional
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- 2021
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37. Dynamical mean field theory algorithm and experiment on quantum computers
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Rungger, I., Fitzpatrick, N, Chen, H., Alderete, C, Apel, H., Cowtan, A, Patterson, A, Muñoz, D., Zhu, Y., Nguyen, N, Grant, E, Chretien, S, Wossnig, L, Linke, N, Duncan, R, University College Dublin [Dublin] (UCD), IBM Corporation, New York, IBM Corporation, GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Département des Technologies Solaires (DTS), Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les nanomatériaux (LITEN), Institut National de L'Energie Solaire (INES), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de L'Energie Solaire (INES), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Imagerie et modélisation Vasculaires, Thoraciques et Cérébrales (MOTIVATE), Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé (CREATIS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de L'Energie Solaire (INES), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Jean Monnet [Saint-Étienne] (UJM)-Hospices Civils de Lyon (HCL)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Jean Monnet [Saint-Étienne] (UJM)-Hospices Civils de Lyon (HCL)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM), Chretien, Stephane, Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Hospices Civils de Lyon (HCL)-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Hospices Civils de Lyon (HCL)-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)
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QA75 ,[SPI.OTHER]Engineering Sciences [physics]/Other ,Quantum Physics ,Condensed Matter - Strongly Correlated Electrons ,[SPI]Engineering Sciences [physics] ,Strongly Correlated Electrons (cond-mat.str-el) ,[SPI] Engineering Sciences [physics] ,[SPI.OTHER] Engineering Sciences [physics]/Other ,FOS: Physical sciences ,Quantum Physics (quant-ph) - Abstract
The developments of quantum computing algorithms and experiments for atomic scale simulations have largely focused on quantum chemistry for molecules, while their application in condensed matter systems is scarcely explored. Here we present a quantum algorithm to perform dynamical mean field theory (DMFT) calculations for condensed matter systems on currently available quantum computers, and demonstrate it on two quantum hardware platforms. DMFT is required to properly describe the large class of materials with strongly correlated electrons. The computation-ally challenging part arises from solving the effective problem of an interacting impurity coupled to a bath, which scales exponentially with system size on conventional computers. An exponential speedup is expected on quantum computers, but the algorithms proposed so far are based on real time evolution of the wavefunction, which requires high-depth circuits and hence very low noise levels in the quantum hardware. Here we propose an alternative approach, which uses the variational quantum eigensolver (VQE) method for ground and excited states to obtain the needed quantities as part of an exact diagonalization impurity solver. We present the algorithm for a two site DMFT system, which we benchmark using simulations on conventional computers as well as experiments on superconducting and trapped ion qubits, demonstrating that this method is suitable for running DMFT calculations on currently available quantum hardware.
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- 2020
38. Conservative oxygen therapy for mechanically ventilated adults with sepsis: a post hoc analysis of data from the intensive care unit randomized trial comparing two approaches to oxygen therapy (ICU-ROX)
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Young, P, Mackle, D, Bellomo, R, Bailey, M, Beasley, R, Deane, A, Eastwood, G, Finfer, S, Freebairn, R, King, V, Linke, N, Litton, E, McArthur, C, McGuinness, S, Panwar, R, Young, P, Mackle, D, Bellomo, R, Bailey, M, Beasley, R, Deane, A, Eastwood, G, Finfer, S, Freebairn, R, King, V, Linke, N, Litton, E, McArthur, C, McGuinness, S, and Panwar, R
- Abstract
PURPOSE: Sepsis is a common reason for intensive care unit (ICU) admission and mortality in ICU patients. Despite increasing interest in treatment strategies limiting oxygen exposure in ICU patients, no trials have compared conservative vs. usual oxygen in patients with sepsis. METHODS: We undertook a post hoc analysis of the 251 patients with sepsis enrolled in a trial that compared conservative oxygen therapy with usual oxygen therapy in 1000 mechanically ventilated ICU patients. The primary end point for the current analysis was 90-day mortality. Key secondary outcomes were cause-specific mortality, ICU and hospital length of stay, ventilator-free days, vasopressor-free days, and the proportion of patients receiving renal replacement therapy in the ICU. RESULTS: Patients with sepsis allocated to conservative oxygen therapy spent less time in the ICU with an SpO2 ≥ 97% (23.5 h [interquartile range (IQR) 8-70] vs. 47 h [IQR 11-93], absolute difference, 23 h; 95% CI 8-38), and more time receiving an FiO2 of 0.21 than patients allocated to usual oxygen therapy (20.5 h [IQR 1-79] vs. 0 h [IQR 0-10], absolute difference, 20 h; 95% CI 14-26). At 90-days, 47 of 130 patients (36.2%) assigned to conservative oxygen and 35 of 120 patients (29.2%) assigned to usual oxygen had died (absolute difference, 7 percentage points; 95% CI - 4.6 to 18.6% points; P = 0.24; interaction P = 0.35 for sepsis vs. non-sepsis). There were no statistically significant differences between groups for secondary outcomes but point estimates of treatment effects consistently favored usual oxygen therapy. CONCLUSIONS: Point estimates for the treatment effect of conservative oxygen therapy on 90-day mortality raise the possibility of clinically important harm with this intervention in patients with sepsis; however, our post hoc analysis was not powered to detect the effects suggested and our data do not exclude clinically important benefit or harm from conservative oxygen therapy in this patient grou
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- 2020
39. Conservative Oxygen Therapy during Mechanical Ventilation in the ICU
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Mackle, D, Bellomo, MNR, Bailey, M, Beasley, R, Deane, A, Eastwood, G, Finfer, S, Freebairn, R, King, V, Linke, N, Litton, E, McArthur, C, McGuinness, S, Panwar, R, Young, P, Mackle, D, Bellomo, MNR, Bailey, M, Beasley, R, Deane, A, Eastwood, G, Finfer, S, Freebairn, R, King, V, Linke, N, Litton, E, McArthur, C, McGuinness, S, Panwar, R, and Young, P
- Abstract
BACKGROUND: Patients who are undergoing mechanical ventilation in the intensive care unit (ICU) often receive a high fraction of inspired oxygen (Fio2) and have a high arterial oxygen tension. The conservative use of oxygen may reduce oxygen exposure, diminish lung and systemic oxidative injury, and thereby increase the number of ventilator-free days (days alive and free from mechanical ventilation). METHODS: We randomly assigned 1000 adult patients who were anticipated to require mechanical ventilation beyond the day after recruitment in the ICU to receive conservative or usual oxygen therapy. In the two groups, the default lower limit for oxygen saturation as measured by pulse oximetry (Spo2) was 90%. In the conservative-oxygen group, the upper limit of the Spo2 alarm was set to sound when the level reached 97%, and the Fio2 was decreased to 0.21 if the Spo2 was above the acceptable lower limit. In the usual-oxygen group, there were no specific measures limiting the Fio2 or the Spo2. The primary outcome was the number of ventilator-free days from randomization until day 28. RESULTS: The number of ventilator-free days did not differ significantly between the conservative-oxygen group and the usual-oxygen group, with a median duration of 21.3 days (interquartile range, 0 to 26.3) and 22.1 days (interquartile range, 0 to 26.2), respectively, for an absolute difference of -0.3 days (95% confidence interval [CI], -2.1 to 1.6; P = 0.80). The conservative-oxygen group spent more time in the ICU with an Fio2 of 0.21 than the usual-oxygen group, with a median duration of 29 hours (interquartile range, 5 to 78) and 1 hour (interquartile range, 0 to 17), respectively (absolute difference, 28 hours; 95% CI, 22 to 34); the conservative-oxygen group spent less time with an Spo2 exceeding 96%, with a duration of 27 hours (interquartile range, 11 to 63.5) and 49 hours (interquartile range, 22 to 112), respectively (absolute difference, 22 hours; 95% CI, 14 to 30). At 180 days, mo
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- 2020
40. Conservative oxygen therapy for mechanically ventilated adults with suspected hypoxic ischaemic encephalopathy
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Young, P, Mackle, D, Bellomo, R, Bailey, M, Beasley, R, Deane, A, Eastwood, G, Finfer, S, Freebairn, R, King, V, Linke, N, Litton, E, McArthur, C, McGuinness, S, Panwar, R, Young, P, Mackle, D, Bellomo, R, Bailey, M, Beasley, R, Deane, A, Eastwood, G, Finfer, S, Freebairn, R, King, V, Linke, N, Litton, E, McArthur, C, McGuinness, S, and Panwar, R
- Abstract
PURPOSE: Liberal use of oxygen may contribute to secondary brain injury in patients with hypoxic-ischaemic encephalopathy (HIE). However, there are limited data on the effect of different oxygen regimens on survival and neurological disability in HIE patients. METHODS: We undertook a post-hoc analysis of the 166 patients with suspected HIE enrolled in a trial comparing conservative oxygen therapy with usual oxygen therapy in 1000 mechanically ventilated ICU patients. The primary endpoint for the current analysis was death or unfavourable neurological outcome at day 180. Key secondary outcomes were day 180 mortality, and cause-specific mortality. RESULTS: Patients with HIE allocated to conservative oxygen spent less time in the ICU with an SpO2 ≥ 97% (26 h [interquartile range (IQR) 13-45 vs. 35 h [IQR 19-70], absolute difference, 9 h; 95% CI - 21.4 to 3.4). A total of 43 of 78 patients (55.1%) assigned to conservative oxygen and 49 of 72 patients (68.1%) assigned to usual oxygen died or had an unfavourable neurological outcome at day 180; odds ratio 0.58; 95% CI 0.3-1.12; P = 0.1 adjusted odds ratio 0.54; 95% CI 0.23-1.26; P = 0.15. A total of 37 of 86 patients (43%) assigned to conservative oxygen and 46 of 78 (59%) assigned to usual oxygen had died by day 180; odds ratio 0.53; 95% CI 0.28-0.98; P = 0.04; adjusted odds ratio 0.56; 95% CI 0.25-1.23; P = 0.15. Cause-specific mortality was similar by treatment group. CONCLUSIONS: Conservative oxygen therapy was not associated with a statistically significant reduction in death or unfavourable neurological outcomes at day 180. The potential for important benefit or harm from conservative oxygen therapy in HIE patients is not excluded by these data.
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- 2020
41. A Survey of Extracorporeal Membrane Oxygenation Practice in 23 Australian Adult Intensive Care Units
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Hodgson, C.L., primary, Linke, N., additional, Fulcher, B., additional, Engeler, D., additional, Anderson, S., additional, Bernard, S., additional, Board, J., additional, Brodie, D., additional, Buhr, H., additional, Burrell, A., additional, Cooper, D.J., additional, Fan, E., additional, Higgins, A., additional, Fraser, J., additional, Gattas, D., additional, Hopper, I., additional, Huckson, S., additional, Litton, E., additional, Nair, P., additional, Orford, N., additional, McGuinness, S., additional, Parke, R., additional, Pilcher, D., additional, Sheldrake, J., additional, Udy, A., additional, Reddi, B., additional, Trapani, A., additional, Stub, D., additional, and Pellegrino, V., additional
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- 2020
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42. Toward convergence of effective-field-theory simulations on digital quantum computers
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Shehab, O., primary, Landsman, K., additional, Nam, Y., additional, Zhu, D., additional, Linke, N. M., additional, Keesan, M., additional, Pooser, R. C., additional, and Monroe, C., additional
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- 2019
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43. Selective upregulation of murine β-defensin 3 after disruption of the permeability barrier: role in defense against Pseudomonas aeruginosa and Staphylococcus aureus: 414
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Schunck, M, Linke, N, Schroeder, J, and Proksch, E
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- 2005
44. High rate deposition and in situ doping of silicon films for solar cells on glass
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Gromball, F., Heemeier, J., Linke, N., Burchert, M., and Müller, J.
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- 2004
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45. Predictors of death and new disability after critical illness: a multicentre prospective cohort study.
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Higgins, A. M., Neto, A. Serpa, Bailey, M., Barrett, J., Bellomo, R., Cooper, D. J., Gabbe, B. J., Linke, N., Myles, P. S., Paton, M., Philpot, S., Shulman, M., Young, M., and Hodgson, C. L.
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CRITICALLY ill ,DISABILITIES ,FORECASTING ,RECEIVER operating characteristic curves ,LONGITUDINAL method ,INTENSIVE care units - Abstract
Purpose: This study aimed to determine the prevalence and predictors of death or new disability following critical illness. Methods: Prospective, multicentre cohort study conducted in six metropolitan intensive care units (ICU). Participants were adults admitted to the ICU who received more than 24 h of mechanical ventilation. The primary outcome was death or new disability at 6 months, with new disability defined by a 10% increase in the WHODAS 2.0. Results: Of 628 patients with the primary outcome available (median age of 62 [49–71] years, 379 [61.0%] had a medical admission and 370 (58.9%) died or developed new disability by 6 months. Independent predictors of death or new disability included age [OR 1.02 (1.01–1.03), P = 0.001], higher severity of illness (APACHE III) [OR 1.02 (1.01–1.03), P < 0.001] and admission diagnosis. Compared to patients with a surgical admission diagnosis, patients with a cardiac arrest [OR (95% CI) 4.06 (1.89–8.68), P < 0.001], sepsis [OR (95% CI) 2.43 (1.32–4.47), P = 0.004], or trauma [OR (95% CI) 6.24 (3.07–12.71), P < 0.001] diagnosis had higher odds of death or new disability, while patients with a lung transplant [OR (95% CI) 0.21 (0.07–0.58), P = 0.003] diagnosis had lower odds. A model including these three variables had good calibration (Brier score 0.20) and acceptable discriminative power with an area under the receiver operating characteristic curve of 0.76 (95% CI 0.72–0.80). Conclusion: Less than half of all patients mechanically ventilated for more than 24 h were alive and free of new disability at 6 months after admission to ICU. A model including age, illness severity and admission diagnosis has acceptable discriminative ability to predict death or new disability at 6 months. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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46. Training of quantum circuits on a hybrid quantum computer
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Zhu, D., primary, Linke, N. M., additional, Benedetti, M., additional, Landsman, K. A., additional, Nguyen, N. H., additional, Alderete, C. H., additional, Perdomo-Ortiz, A., additional, Korda, N., additional, Garfoot, A., additional, Brecque, C., additional, Egan, L., additional, Perdomo, O., additional, and Monroe, C., additional
- Published
- 2019
- Full Text
- View/download PDF
47. Two-qubit entangling gates within arbitrarily long chains of trapped ions
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Landsman, K. A., primary, Wu, Y., additional, Leung, P. H., additional, Zhu, D., additional, Linke, N. M., additional, Brown, K. R., additional, Duan, L., additional, and Monroe, C., additional
- Published
- 2019
- Full Text
- View/download PDF
48. Quantum Computing and Simulation with Trapped Atomic Ions
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Pagano, G., primary, Becker, P., additional, Carter, A., additional, Cetina, M., additional, Collins, K., additional, Crocker, C., additional, Egan, L., additional, Goldman, M., additional, Gorshkov, A.V., additional, Kyprianidis, A., additional, Kaplan, H., additional, Landsman, K., additional, Lichtman, M., additional, Linke, N., additional, Liu, F., additional, Risinger, D., additional, Sosnova, K., additional, Tan, W. L., additional, Zhu, D., additional, and Monroe, C., additional
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- 2019
- Full Text
- View/download PDF
49. Measuring the Rényi entropy of a two-site Fermi-Hubbard model on a trapped ion quantum computer
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Linke, N. M., primary, Johri, S., additional, Figgatt, C., additional, Landsman, K. A., additional, Matsuura, A. Y., additional, and Monroe, C., additional
- Published
- 2018
- Full Text
- View/download PDF
50. Background-free detection and mixed-species crystals in micro- and macroscopic ion-traps for scalable QIP
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Linke, N and Lucas, D
- Subjects
Physics ,Atomic and laser physics - Abstract
Scalability and the implementation of fault tolerant quantum gates are the two main challenges which must be overcome in order to unlock the vast potential of quantum computing. This thesis describes work with calcium ions trapped in both microscopic and macroscopic linear Paul traps addressing both of these issues. We describe the assembly of a microstructured multi-zone ion trap which forms part of our group's contribution to the European "Microtrap" collaboration. We report the successful trapping of ions and characterization of the trap as well as a measurement of the heating rate. In miniaturized trap structures such as this one, background scattered light from the cooling beam causes difficulties. We introduce and demonstrate experimentally two techniques to overcome this problem. The first achieves background-free detection of ions using different repumping methods to enable the filtering out of the excitation wavelength. The second makes possible background-free readout of trapped ion qubits by separating in time the excitation and detection steps The second half of the thesis describes our experimental efforts towards implementing a two-qubit entangling gate with a mixed-species crystal. We describe the setup and characterization of a new macroscopic trap including the trapping and coherent manipulation of the internal states of both 40Ca+ and 43Ca+ ions. We accomplish the simultaneous independent readout of two qubits implemented in a 40Ca+ - 43Ca+ ion pair. We also present the setup and characterization of two injection-locked frequency-doubled Raman lasers and demonstrate coherent manipulation as well as a measurement of the off-resonant photon scattering error they introduce. Finally, we use them to achieve sideband cooling to the motional ground state of a mixed species ion crystal.
- Published
- 2017
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