2020 |
E. Flurin, L. S. Martin, S. Hacohen-Gourgy,, I. Siddiqi Using a Recurrent Neural Network to Reconstruct Quantum Dynamics of a Superconducting Qubit from Physical Observations (Journal Article) Phys. Rev. X, 2020. (Abstract | Links | BibTeX | Tags: Superconducting Qubit) @article{Flurin2020, title = {Using a Recurrent Neural Network to Reconstruct Quantum Dynamics of a Superconducting Qubit from Physical Observations}, author = {E. Flurin, L. S. Martin, S. Hacohen-Gourgy, and I. Siddiqi }, url = {https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011006}, year = {2020}, date = {2020-01-09}, journal = {Phys. Rev. X}, abstract = {At its core, quantum mechanics is a theory developed to describe fundamental observations in the spectroscopy of solids and gases. Despite these practical roots, however, quantum theory is infamous for being highly counterintuitive, largely due to its intrinsically probabilistic nature. Neural networks have recently emerged as a powerful tool that can extract nontrivial correlations in vast datasets. These networks routinely outperform state-of-the-art techniques in language translation, medical diagnosis, and image recognition. It remains to be seen if neural networks can be trained to predict stochastic quantum evolution without a priori specifying the rules of quantum theory. Here, we demonstrate that a recurrent neural network can be trained in real time to infer the individual quantum trajectories associated with the evolution of a superconducting qubit under unitary evolution, decoherence, and continuous measurement from physical observations only. The network extracts the system Hamiltonian, measurement operators, and physical parameters. It is also able to perform tomography of an unknown initial state without any prior calibration. This method has the potential to greatly simplify and enhance tasks in quantum systems such as noise characterization, parameter estimation, feedback, and optimization of quantum control. }, keywords = {Superconducting Qubit}, pubstate = {published}, tppubtype = {article} } At its core, quantum mechanics is a theory developed to describe fundamental observations in the spectroscopy of solids and gases. Despite these practical roots, however, quantum theory is infamous for being highly counterintuitive, largely due to its intrinsically probabilistic nature. Neural networks have recently emerged as a powerful tool that can extract nontrivial correlations in vast datasets. These networks routinely outperform state-of-the-art techniques in language translation, medical diagnosis, and image recognition. It remains to be seen if neural networks can be trained to predict stochastic quantum evolution without a priori specifying the rules of quantum theory. Here, we demonstrate that a recurrent neural network can be trained in real time to infer the individual quantum trajectories associated with the evolution of a superconducting qubit under unitary evolution, decoherence, and continuous measurement from physical observations only. The network extracts the system Hamiltonian, measurement operators, and physical parameters. It is also able to perform tomography of an unknown initial state without any prior calibration. This method has the potential to greatly simplify and enhance tasks in quantum systems such as noise characterization, parameter estimation, feedback, and optimization of quantum control. |
2019 |
Juan Atalaya, Shay Hacohen-Gourgy, Irfan Siddiqi,, Alexander N. Korotkov Correlators Exceeding One in Continuous Measurements of Superconducting Qubits (Journal Article) Phys. Rev. Lett. , 2019. (Abstract | Links | BibTeX | Tags: Superconducting Qubits) @article{Atalaya2019, title = {Correlators Exceeding One in Continuous Measurements of Superconducting Qubits}, author = {Juan Atalaya, Shay Hacohen-Gourgy, Irfan Siddiqi, and Alexander N. Korotkov }, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.223603}, year = {2019}, date = {2019-06-07}, journal = {Phys. Rev. Lett. }, abstract = {We consider the effect of phase backaction on the correlator ⟨I(t)I(t+τ)⟩ for the output signal I(t) from continuous measurement of a qubit. We demonstrate that the interplay between informational and phase backactions in the presence of Rabi oscillations can lead to the correlator becoming larger than 1, even though |⟨I⟩|≤1. The correlators can be calculated using the generalized “collapse recipe,” which we validate using the quantum Bayesian formalism. The recipe can be further generalized to the case of multitime correlators and arbitrary number of detectors, measuring non-commuting qubit observables. The theory agrees well with experimental results for continuous measurement of a transmon qubit. The experimental correlator exceeds the bound of 1 for a sufficiently large angle between the amplified and informational quadratures, causing the phase backaction. The demonstrated effect can be used to calibrate the quadrature misalignment. }, keywords = {Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } We consider the effect of phase backaction on the correlator ⟨I(t)I(t+τ)⟩ for the output signal I(t) from continuous measurement of a qubit. We demonstrate that the interplay between informational and phase backactions in the presence of Rabi oscillations can lead to the correlator becoming larger than 1, even though |⟨I⟩|≤1. The correlators can be calculated using the generalized “collapse recipe,” which we validate using the quantum Bayesian formalism. The recipe can be further generalized to the case of multitime correlators and arbitrary number of detectors, measuring non-commuting qubit observables. The theory agrees well with experimental results for continuous measurement of a transmon qubit. The experimental correlator exceeds the bound of 1 for a sufficiently large angle between the amplified and informational quadratures, causing the phase backaction. The demonstrated effect can be used to calibrate the quadrature misalignment. |
A. Eddins, J. M. Kreikebaum, D. M. Toyli, E. M. Levenson-Falk, A. Dove, W. P. Livingston, B. A. Levitan, L. C. G. Govia, A. A. Clerk,, I. Siddiqi High-Efficiency Measurement of an Artificial Atom Embedded in a Parametric Amplifier (Journal Article) Phys. Rev. X, 2019. (Abstract | Links | BibTeX | Tags: Parametric Amplifier) @article{Eddins2019, title = {High-Efficiency Measurement of an Artificial Atom Embedded in a Parametric Amplifier}, author = {A. Eddins, J. M. Kreikebaum, D. M. Toyli, E. M. Levenson-Falk, A. Dove, W. P. Livingston, B. A. Levitan, L. C. G. Govia, A. A. Clerk, and I. Siddiqi}, url = {https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.011004}, year = {2019}, date = {2019-01-07}, journal = {Phys. Rev. X}, abstract = {A crucial limit to measurement efficiencies of superconducting circuits comes from losses involved when coupling to an external quantum amplifier. Here, we realize a device circumventing this problem by directly embedding an artificial atom, comprised of a transmon qubit, within a flux-pumped Josephson parametric amplifier. This configuration is able to enhance dispersive measurement without exposing the qubit to appreciable excess backaction. Near-optimal backaction is obtained by engineering the circuit to permit high-power operation that reduces information loss to unmonitored channels associated with the amplification and squeezing of quantum noise. By mitigating the effects of off-chip losses downstream, the on-chip gain of this device produces end-to-end measurement efficiencies of up to 80%. Our theoretical model accurately describes the observed interplay of gain and measurement backaction and delineates the parameter space for future improvement. The device is compatible with standard fabrication and measurement techniques and, thus, provides a route for definitive investigations of fundamental quantum effects and quantum control protocols.}, keywords = {Parametric Amplifier}, pubstate = {published}, tppubtype = {article} } A crucial limit to measurement efficiencies of superconducting circuits comes from losses involved when coupling to an external quantum amplifier. Here, we realize a device circumventing this problem by directly embedding an artificial atom, comprised of a transmon qubit, within a flux-pumped Josephson parametric amplifier. This configuration is able to enhance dispersive measurement without exposing the qubit to appreciable excess backaction. Near-optimal backaction is obtained by engineering the circuit to permit high-power operation that reduces information loss to unmonitored channels associated with the amplification and squeezing of quantum noise. By mitigating the effects of off-chip losses downstream, the on-chip gain of this device produces end-to-end measurement efficiencies of up to 80%. Our theoretical model accurately describes the observed interplay of gain and measurement backaction and delineates the parameter space for future improvement. The device is compatible with standard fabrication and measurement techniques and, thus, provides a route for definitive investigations of fundamental quantum effects and quantum control protocols. |
2018 |
J. I. Colless, V. V. Ramasesh, D. Dahlen, M. S. Blok, M. E. Kimchi-Schwartz, J. R. McClean, J. Carter, W. A. de Jong,, I. Siddiqi Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm (Journal Article) Phys. Rev. X, 2018. (Abstract | Links | BibTeX | Tags: Molecular Spectra) @article{Colless2018, title = {Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm}, author = {J. I. Colless, V. V. Ramasesh, D. Dahlen, M. S. Blok, M. E. Kimchi-Schwartz, J. R. McClean, J. Carter, W. A. de Jong, and I. Siddiqi }, url = {https://journals.aps.org/prx/abstract/10.1103/PhysRevX.8.011021}, year = {2018}, date = {2018-02-12}, journal = {Phys. Rev. X}, abstract = {Harnessing the full power of nascent quantum processors requires the efficient management of a limited number of quantum bits with finite coherent lifetimes. Hybrid algorithms, such as the variational quantum eigensolver (VQE), leverage classical resources to reduce the required number of quantum gates. Experimental demonstrations of VQE have resulted in calculation of Hamiltonian ground states, and a new theoretical approach based on a quantum subspace expansion (QSE) has outlined a procedure for determining excited states that are central to dynamical processes. We use a superconducting-qubit-based processor to apply the QSE approach to the H2 molecule, extracting both ground and excited states without the need for auxiliary qubits or additional minimization. Further, we show that this extended protocol can mitigate the effects of incoherent errors, potentially enabling larger-scale quantum simulations without the need for complex error-correction techniques.}, keywords = {Molecular Spectra}, pubstate = {published}, tppubtype = {article} } Harnessing the full power of nascent quantum processors requires the efficient management of a limited number of quantum bits with finite coherent lifetimes. Hybrid algorithms, such as the variational quantum eigensolver (VQE), leverage classical resources to reduce the required number of quantum gates. Experimental demonstrations of VQE have resulted in calculation of Hamiltonian ground states, and a new theoretical approach based on a quantum subspace expansion (QSE) has outlined a procedure for determining excited states that are central to dynamical processes. We use a superconducting-qubit-based processor to apply the QSE approach to the H2 molecule, extracting both ground and excited states without the need for auxiliary qubits or additional minimization. Further, we show that this extended protocol can mitigate the effects of incoherent errors, potentially enabling larger-scale quantum simulations without the need for complex error-correction techniques. |
Juan Atalaya, Shay Hacohen-Gourgy, Leigh S. Martin, Irfan Siddiqi,, Alexander N. Korotkov Multitime correlators in continuous measurement of qubit observables (Journal Article) Phys. Rev. A, 2018. (Abstract | Links | BibTeX | Tags: correlators) @article{Atalaya2018, title = {Multitime correlators in continuous measurement of qubit observables}, author = {Juan Atalaya, Shay Hacohen-Gourgy, Leigh S. Martin, Irfan Siddiqi, and Alexander N. Korotkov }, url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.020104}, year = {2018}, date = {2018-02-09}, journal = {Phys. Rev. A}, abstract = {We consider multitime correlators for output signals from linear detectors, continuously measuring several qubit observables at the same time. Using the quantum Bayesian formalism, we show that for unital (symmetric) evolution in the absence of phase backaction, an N-time correlator can be expressed as a product of two-time correlators when N is even. For odd N, there is a similar factorization, which also includes a single-time average. Theoretical predictions agree well with experimental results for two detectors, which simultaneously measure noncommuting qubit observables. }, keywords = {correlators}, pubstate = {published}, tppubtype = {article} } We consider multitime correlators for output signals from linear detectors, continuously measuring several qubit observables at the same time. Using the quantum Bayesian formalism, we show that for unital (symmetric) evolution in the absence of phase backaction, an N-time correlator can be expressed as a product of two-time correlators when N is even. For odd N, there is a similar factorization, which also includes a single-time average. Theoretical predictions agree well with experimental results for two detectors, which simultaneously measure noncommuting qubit observables. |
A. Eddins, S. Schreppler, D. M. Toyli, L. S. Martin, S. Hacohen-Gourgy, L. C. G. Govia, H. Ribeiro, A. A. Clerk,, I. Siddiqi Stroboscopic Qubit Measurement with Squeezed Illumination (Journal Article) Phys. Rev. Lett., 2018. (Abstract | Links | BibTeX | Tags: Qubit) @article{Eddins2018, title = {Stroboscopic Qubit Measurement with Squeezed Illumination}, author = {A. Eddins, S. Schreppler, D. M. Toyli, L. S. Martin, S. Hacohen-Gourgy, L. C. G. Govia, H. Ribeiro, A. A. Clerk, and I. Siddiqi }, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.040505}, year = {2018}, date = {2018-01-26}, journal = {Phys. Rev. Lett.}, abstract = {Microwave squeezing represents the ultimate sensitivity frontier for superconducting qubit measurement. However, measurement enhancement has remained elusive, in part because integration with standard dispersive readout pollutes the signal channel with antisqueezed noise. Here we induce a stroboscopic light-matter coupling with superior squeezing compatibility, and observe an increase in the final signal-to-noise ratio of 24%. Squeezing the orthogonal phase slows measurement-induced dephasing by a factor of 1.8. This scheme provides a means to the practical application of squeezing for qubit measurement. }, keywords = {Qubit}, pubstate = {published}, tppubtype = {article} } Microwave squeezing represents the ultimate sensitivity frontier for superconducting qubit measurement. However, measurement enhancement has remained elusive, in part because integration with standard dispersive readout pollutes the signal channel with antisqueezed noise. Here we induce a stroboscopic light-matter coupling with superior squeezing compatibility, and observe an increase in the final signal-to-noise ratio of 24%. Squeezing the orthogonal phase slows measurement-induced dephasing by a factor of 1.8. This scheme provides a means to the practical application of squeezing for qubit measurement. |
Areeya Chantasri, Juan Atalaya, Shay Hacohen-Gourgy, Leigh S. Martin, Irfan Siddiqi,, Andrew N. Jordan Simultaneous continuous measurement of noncommuting observables: Quantum state correlations (Journal Article) Phys. Rev. A , 2018. (Abstract | Links | BibTeX | Tags: Quantum State) @article{Chantasri2018, title = {Simultaneous continuous measurement of noncommuting observables: Quantum state correlations}, author = {Areeya Chantasri, Juan Atalaya, Shay Hacohen-Gourgy, Leigh S. Martin, Irfan Siddiqi, and Andrew N. Jordan}, url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.012118}, year = {2018}, date = {2018-01-17}, journal = {Phys. Rev. A }, abstract = {We consider the temporal correlations of the quantum state of a qubit subject to simultaneous continuous measurement of two noncommuting qubit observables. Such qubit state correlators are defined for an ensemble of qubit trajectories, which has the same fixed initial state and can also be optionally constrained by a fixed final state. We develop a stochastic path integral description for the continuous quantum measurement and use it to calculate the considered correlators. Exact analytic results are possible in the case of ideal measurements of equal strength and are also shown to agree with solutions obtained using the Fokker-Planck equation. For a more general case with decoherence effects and inefficiency, we use a diagrammatic approach to find the correlators perturbatively in the quantum efficiency. We also calculate the state correlators for the quantum trajectories which are extracted from readout signals measured in a transmon qubit experiment, by means of the quantum Bayesian state update. We find an excellent agreement between the correlators based on the experimental data and those obtained from our analytical and numerical results. }, keywords = {Quantum State}, pubstate = {published}, tppubtype = {article} } We consider the temporal correlations of the quantum state of a qubit subject to simultaneous continuous measurement of two noncommuting qubit observables. Such qubit state correlators are defined for an ensemble of qubit trajectories, which has the same fixed initial state and can also be optionally constrained by a fixed final state. We develop a stochastic path integral description for the continuous quantum measurement and use it to calculate the considered correlators. Exact analytic results are possible in the case of ideal measurements of equal strength and are also shown to agree with solutions obtained using the Fokker-Planck equation. For a more general case with decoherence effects and inefficiency, we use a diagrammatic approach to find the correlators perturbatively in the quantum efficiency. We also calculate the state correlators for the quantum trajectories which are extracted from readout signals measured in a transmon qubit experiment, by means of the quantum Bayesian state update. We find an excellent agreement between the correlators based on the experimental data and those obtained from our analytical and numerical results. |
S. Hacohen-Gourgy, L. P. García-Pintos, L. S. Martin, J. Dressel,, I. Siddiqi Incoherent Qubit Control Using the Quantum Zeno Effect (Journal Article) Phys. Rev. Lett., 2018. (Abstract | Links | BibTeX | Tags: Quantum Zeno) @article{Hacohen-Gourgy2018, title = {Incoherent Qubit Control Using the Quantum Zeno Effect}, author = {S. Hacohen-Gourgy, L. P. Garc\^{i}a-Pintos, L. S. Martin, J. Dressel, and I. Siddiqi}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.020505}, year = {2018}, date = {2018-01-10}, journal = {Phys. Rev. Lett.}, abstract = {The quantum Zeno effect is the suppression of Hamiltonian evolution by repeated observation, which pins the system to an eigenstate of the measurement observable. Using measurement alone, control of the state can be achieved if the observable is slowly varied, so that the state tracks the now time-dependent eigenstate. We demonstrate this using a circuit-QED readout technique that couples to a dynamically controllable observable of a qubit. Continuous monitoring of the measurement record allows us to detect an escape from the eigenstate, thus serving as a built-in form of error detection. We show this by postselecting on realizations with high fidelity with respect to the target state. Our dynamical measurement operator technique offers a new tool for numerous forms of quantum feedback protocols, including adaptive measurements and rapid state purification.}, keywords = {Quantum Zeno}, pubstate = {published}, tppubtype = {article} } The quantum Zeno effect is the suppression of Hamiltonian evolution by repeated observation, which pins the system to an eigenstate of the measurement observable. Using measurement alone, control of the state can be achieved if the observable is slowly varied, so that the state tracks the now time-dependent eigenstate. We demonstrate this using a circuit-QED readout technique that couples to a dynamically controllable observable of a qubit. Continuous monitoring of the measurement record allows us to detect an escape from the eigenstate, thus serving as a built-in form of error detection. We show this by postselecting on realizations with high fidelity with respect to the target state. Our dynamical measurement operator technique offers a new tool for numerous forms of quantum feedback protocols, including adaptive measurements and rapid state purification. |
2017 |
Samuel Boutin, David M. Toyli, Aditya V. Venkatramani, Andrew W. Eddins, Irfan Siddiqi,, Alexandre Blais Effect of Higher-Order Nonlinearities on Amplification and Squeezing in Josephson Parametric Amplifiers (Journal Article) Phys. Rev. Applied, 2017. (Abstract | Links | BibTeX | Tags: Parametric Amplifiers) @article{Boutin2017, title = {Effect of Higher-Order Nonlinearities on Amplification and Squeezing in Josephson Parametric Amplifiers}, author = {Samuel Boutin, David M. Toyli, Aditya V. Venkatramani, Andrew W. Eddins, Irfan Siddiqi, and Alexandre Blais}, url = {https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.8.054030 }, year = {2017}, date = {2017-11-15}, journal = {Phys. Rev. Applied}, abstract = {Single-mode Josephson-junction-based parametric amplifiers are often modeled as perfect amplifiers and squeezers. We show that in practice, the gain, quantum efficiency, and output field squeezing of these devices are limited by usually neglected higher-order corrections to the idealized model. To arrive at this result, we derive the leading corrections to the lumped-element Josephson parametric amplifier of three common pumping schemes: monochromatic current pump, bichromatic current pump, and monochromatic flux pump. We show that the leading correction for the last two schemes is a single Kerr-type quartic term, while the first scheme contains additional cubic terms. In all cases, we find that the corrections are detrimental to squeezing. In addition, we show that the Kerr correction leads to a strongly phase-dependent reduction of the quantum efficiency of a phase-sensitive measurement. Finally, we quantify the departure from the ideal Gaussian character of the filtered output field from numerical calculation of third- and fourth-order cumulants. Our results show that while a Gaussian output field is expected for an ideal Josephson parametric amplifier, higher-order corrections lead to non-Gaussian effects which increase with both gain and nonlinearity strength. This theoretical study is complemented by experimental characterization of the output field of a flux-driven Josephson parametric amplifier. In addition to a measurement of the squeezing level of the filtered output field, the Husimi Q function of the output field is imaged by the use of a deconvolution technique and compared to numerical results. This work establishes nonlinear corrections to the standard degenerate parametric amplifier model as an important contribution to the Josephson parametric amplifier’s squeezing and noise performance.}, keywords = {Parametric Amplifiers}, pubstate = {published}, tppubtype = {article} } Single-mode Josephson-junction-based parametric amplifiers are often modeled as perfect amplifiers and squeezers. We show that in practice, the gain, quantum efficiency, and output field squeezing of these devices are limited by usually neglected higher-order corrections to the idealized model. To arrive at this result, we derive the leading corrections to the lumped-element Josephson parametric amplifier of three common pumping schemes: monochromatic current pump, bichromatic current pump, and monochromatic flux pump. We show that the leading correction for the last two schemes is a single Kerr-type quartic term, while the first scheme contains additional cubic terms. In all cases, we find that the corrections are detrimental to squeezing. In addition, we show that the Kerr correction leads to a strongly phase-dependent reduction of the quantum efficiency of a phase-sensitive measurement. Finally, we quantify the departure from the ideal Gaussian character of the filtered output field from numerical calculation of third- and fourth-order cumulants. Our results show that while a Gaussian output field is expected for an ideal Josephson parametric amplifier, higher-order corrections lead to non-Gaussian effects which increase with both gain and nonlinearity strength. This theoretical study is complemented by experimental characterization of the output field of a flux-driven Josephson parametric amplifier. In addition to a measurement of the squeezing level of the filtered output field, the Husimi Q function of the output field is imaged by the use of a deconvolution technique and compared to numerical results. This work establishes nonlinear corrections to the standard degenerate parametric amplifier model as an important contribution to the Josephson parametric amplifier’s squeezing and noise performance. |
E. Flurin, V. V. Ramasesh, S. Hacohen-Gourgy, L. S. Martin, N. Y. Yao,, I. Siddiqi Observing Topological Invariants Using Quantum Walks in Superconducting Circuits (Journal Article) Phys. Rev. X, 2017. (Abstract | Links | BibTeX | Tags: Quantum Walks) @article{Flurin2017, title = {Observing Topological Invariants Using Quantum Walks in Superconducting Circuits}, author = {E. Flurin, V. V. Ramasesh, S. Hacohen-Gourgy, L. S. Martin, N. Y. Yao, and I. Siddiqi}, url = {https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.031023 https://arxiv.org/abs/1609.09504}, year = {2017}, date = {2017-08-03}, journal = {Phys. Rev. X}, abstract = {The direct measurement of topological invariants in both engineered and naturally occurring quantum materials is a key step in classifying quantum phases of matter. Here, we motivate a toolbox based on time-dependent quantum walks as a method to digitally simulate single-particle topological band structures. Using a superconducting qubit dispersively coupled to a microwave cavity, we implement two classes of split-step quantum walks and directly measure the topological invariant (winding number) associated with each. The measurement relies upon interference between two components of a cavity Schr\"{o}dinger cat state and highlights a novel refocusing technique, which allows for the direct implementation of a digital version of Bloch oscillations. As the walk is performed in phase space, our scheme can be extended to higher synthetic dimensions by adding additional microwave cavities, whereby superconducting circuit-based simulations can probe topological phases ranging from the quantum-spin Hall effect to the Hopf insulator.}, keywords = {Quantum Walks}, pubstate = {published}, tppubtype = {article} } The direct measurement of topological invariants in both engineered and naturally occurring quantum materials is a key step in classifying quantum phases of matter. Here, we motivate a toolbox based on time-dependent quantum walks as a method to digitally simulate single-particle topological band structures. Using a superconducting qubit dispersively coupled to a microwave cavity, we implement two classes of split-step quantum walks and directly measure the topological invariant (winding number) associated with each. The measurement relies upon interference between two components of a cavity Schrödinger cat state and highlights a novel refocusing technique, which allows for the direct implementation of a digital version of Bloch oscillations. As the walk is performed in phase space, our scheme can be extended to higher synthetic dimensions by adding additional microwave cavities, whereby superconducting circuit-based simulations can probe topological phases ranging from the quantum-spin Hall effect to the Hopf insulator. |
Ramasesh, V. V., Flurin, E., Rudner, M. S., Siddiqi, I., Yao, N. Y. Direct Probe of Topological Invariants Using Bloch Oscillating Quantum Walks (Journal Article) Phys. Rev. Lett., 2017. (Abstract | Links | BibTeX | Tags: Quantum Walk) @article{Ramasesh2016, title = {Direct Probe of Topological Invariants Using Bloch Oscillating Quantum Walks}, author = {Ramasesh, V. V. and Flurin, E. and Rudner, M. S. and Siddiqi, I. and Yao, N. Y.}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.130501 https://arxiv.org/abs/1609.09504v1}, year = {2017}, date = {2017-03-27}, journal = {Phys. Rev. Lett.}, abstract = {The topology of a single-particle band structure plays a fundamental role in understanding a multitude of physical phenomena. Motivated by the connection between quantum walks and such topological band structures, we demonstrate that a simple time-dependent, Bloch-oscillating quantum walk enables the direct measurement of topological invariants. We consider two classes of one-dimensional quantum walks and connect the global phase imprinted on the walker with its refocusing behavior. By disentangling the dynamical and geometric contributions to this phase we describe a general strategy to measure the topological invariant in these quantum walks. As an example, we propose an experimental protocol in a circuit QED architecture where a superconducting transmon qubit plays the role of the coin, while the quantum walk takes place in the phase space of a cavity.}, keywords = {Quantum Walk}, pubstate = {published}, tppubtype = {article} } The topology of a single-particle band structure plays a fundamental role in understanding a multitude of physical phenomena. Motivated by the connection between quantum walks and such topological band structures, we demonstrate that a simple time-dependent, Bloch-oscillating quantum walk enables the direct measurement of topological invariants. We consider two classes of one-dimensional quantum walks and connect the global phase imprinted on the walker with its refocusing behavior. By disentangling the dynamical and geometric contributions to this phase we describe a general strategy to measure the topological invariant in these quantum walks. As an example, we propose an experimental protocol in a circuit QED architecture where a superconducting transmon qubit plays the role of the coin, while the quantum walk takes place in the phase space of a cavity. |
2016 |
Flurin, E., Ramasesh, V. V., Hacohen-Gourgy, S., Martin, L., Yao, N. Y., Siddiqi, I. Observing Topological Invariants Using Quantum Walk in Superconducting Circuits (Journal Article) 2016. (Abstract | Links | BibTeX | Tags: Quantum Walk) @article{Flurin2016, title = {Observing Topological Invariants Using Quantum Walk in Superconducting Circuits}, author = {Flurin, E. and Ramasesh, V. V. and Hacohen-Gourgy, S. and Martin, L. and Yao, N. Y. and Siddiqi, I.}, url = {https://arxiv.org/abs/1610.03069}, year = {2016}, date = {2016-10-10}, abstract = {The direct measurement of topological invariants in both engineered and naturally occurring quantum materials is a key step in classifying quantum phases of matter. Here we motivate a toolbox based on time-dependent quantum walks as a method to digitally simulate single-particle topological band structures. Using a superconducting qubit dispersively coupled to a microwave cavity, we implement two classes of split-step quantum walks and directly measure the topological invariant (winding number) associated with each. The measurement relies upon interference between two components of a cavity Schrodinger cat state and highlights a novel refocusing technique which allows for the direct implementation of a digital version of Bloch oscillations. Our scheme can readily be extended to higher dimensions, whereby quantum walk-based simulations can probe topological phases ranging from the quantum spin Hall effect to the Hopf insulator.}, keywords = {Quantum Walk}, pubstate = {published}, tppubtype = {article} } The direct measurement of topological invariants in both engineered and naturally occurring quantum materials is a key step in classifying quantum phases of matter. Here we motivate a toolbox based on time-dependent quantum walks as a method to digitally simulate single-particle topological band structures. Using a superconducting qubit dispersively coupled to a microwave cavity, we implement two classes of split-step quantum walks and directly measure the topological invariant (winding number) associated with each. The measurement relies upon interference between two components of a cavity Schrodinger cat state and highlights a novel refocusing technique which allows for the direct implementation of a digital version of Bloch oscillations. Our scheme can readily be extended to higher dimensions, whereby quantum walk-based simulations can probe topological phases ranging from the quantum spin Hall effect to the Hopf insulator. |
Hacohen-Gourgy, S., S. Martin, L., Flurin, E., Ramasesh, V. V., Whaley, K. B., Siddiqi, I. Dynamics of simultaneously measured non-commuting observables (Journal Article) Nature, (19762), 2016. (Links | BibTeX | Tags: circuit quantum electrodynamics, quantum feedback, Superconducting Qubits) @article{Hacohen-Gourgy2016, title = {Dynamics of simultaneously measured non-commuting observables}, author = {Hacohen-Gourgy, S. and S. Martin, L. and Flurin, E. and Ramasesh, V. V. and Whaley, K. B. and Siddiqi, I.}, url = {http://www.nature.com/nature/journal/vaop/ncurrent/full/nature19762.html http://arxiv.org/abs/1608.06652 http://www.nature.com/articles/nature19762.epdf?author_access_token=93YEEjSwuQyWstVt5yP7a9RgN0jAjWel9jnR3ZoTv0MF3PwSCTmVtXRTm4UjZbi_FeGpR3bXa5cl-1O1fNJul_tlLi9d1QWBfTiBpkeLnBOOBb71gAlLTF2LmNeGqZTH}, doi = {10.1038/nature19762}, year = {2016}, date = {2016-10-05}, journal = {Nature}, number = {19762}, keywords = {circuit quantum electrodynamics, quantum feedback, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Levenson-Falk, E. M., Antler, N., Siddiqi, I. Dispersive nanoSQUID magnetometry (Journal Article) Superconductor Science and Technology, 29 (11), pp. 113003, 2016. (Abstract | Links | BibTeX | Tags: SQUID) @article{0953-2048-29-11-113003, title = {Dispersive nanoSQUID magnetometry}, author = {Levenson-Falk, E. M. and Antler, N. and Siddiqi, I.}, url = {http://stacks.iop.org/0953-2048/29/i=11/a=113003}, year = {2016}, date = {2016-09-26}, journal = {Superconductor Science and Technology}, volume = {29}, number = {11}, pages = {113003}, abstract = {We describe the theory and implementation of a dispersive magnetometer based on an aluminum nanoSQUID. The nanoSQUID consists of a superconducting loop interrupted by two variable-thickness weak-link nanobridge Josephson junctions. When the nanoSQUID is placed in parallel with a lumped-element capacitor, it acts as the inductive element in a resonant tank circuit. By performing microwave reflectometry on the circuit, the SQUID inductance can be measured, providing a sensitive meter of the flux threading the SQUID loop. In this review we provide the theoretical basis for the device, describe design and operation considerations, and present characterization results on several devices.}, keywords = {SQUID}, pubstate = {published}, tppubtype = {article} } We describe the theory and implementation of a dispersive magnetometer based on an aluminum nanoSQUID. The nanoSQUID consists of a superconducting loop interrupted by two variable-thickness weak-link nanobridge Josephson junctions. When the nanoSQUID is placed in parallel with a lumped-element capacitor, it acts as the inductive element in a resonant tank circuit. By performing microwave reflectometry on the circuit, the SQUID inductance can be measured, providing a sensitive meter of the flux threading the SQUID loop. In this review we provide the theoretical basis for the device, describe design and operation considerations, and present characterization results on several devices. |
Kreikebaum, J. M., Dove, A., Livingston, W., Kim, E., Siddiqi, I. Optimization of infrared and magnetic shielding of superconducting TiN and Al coplanar microwave resonators (Journal Article) Superconductor Science and Technology, 29 (10), pp. 104002, 2016. (Links | BibTeX | Tags: Cryogenic Microwave Technology) @article{0953-2048-29-10-104002, title = {Optimization of infrared and magnetic shielding of superconducting TiN and Al coplanar microwave resonators}, author = {Kreikebaum, J. M. and Dove, A. and Livingston, W. and Kim, E. and Siddiqi, I.}, url = {http://stacks.iop.org/0953-2048/29/i=10/a=104002}, year = {2016}, date = {2016-08-12}, journal = {Superconductor Science and Technology}, volume = {29}, number = {10}, pages = {104002}, keywords = {Cryogenic Microwave Technology}, pubstate = {published}, tppubtype = {article} } |
Schwartz, M. E., Martin, L., Flurin, E., Aron, C., Kulkarni, M., Tureci, H. E., Siddiqi, I. Stabilizing Entanglement via Symmetry-Selective Bath Engineering in Superconducting Qubits (Journal Article) Phys. Rev. Lett., 116 , pp. 240503, 2016. (Links | BibTeX | Tags: Bath Engineering, Superconducting Qubits) @article{PhysRevLett.116.240503, title = {Stabilizing Entanglement via Symmetry-Selective Bath Engineering in Superconducting Qubits}, author = {Schwartz, M. E. and Martin, L. and Flurin, E. and Aron, C. and Kulkarni, M. and Tureci, H. E. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.116.240503}, doi = {10.1103/PhysRevLett.116.240503}, year = {2016}, date = {2016-06-01}, journal = {Phys. Rev. Lett.}, volume = {116}, pages = {240503}, publisher = {American Physical Society}, keywords = {Bath Engineering, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Slichter, D. H., Müller, C., Vijay, R., Weber, S. J., Blais, A., Siddiqi, I. Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics (Journal Article) New Journal of Physics, 2016. (Abstract | Links | BibTeX | Tags: circuit quantum electrodynamics) @article{Slichter2015, title = {Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics}, author = {Slichter, D. H. and M\"{u}ller, C. and Vijay, R. and Weber, S. J. and Blais, A. and Siddiqi, I.}, url = {http://iopscience.iop.org/article/10.1088/1367-2630/18/5/053031/meta}, year = {2016}, date = {2016-05-17}, journal = {New Journal of Physics}, abstract = {We observe the quantum Zeno effect{\textemdash}where the act of measurement slows the rate of quantum state transitions{\textemdash}in a superconducting qubit using linear circuit quantum electrodynamics readout and a near-quantum-limited following amplifier. Under simultaneous strong measurement and qubit drive, the qubit undergoes a series of quantum jumps between states. These jumps are visible in the experimental measurement record and are analyzed using maximum likelihood estimation to determine qubit transition rates. The observed rates agree with both analytical predictions and numerical simulations. The analysis methods are suitable for processing general noisy random telegraph signals.}, keywords = {circuit quantum electrodynamics}, pubstate = {published}, tppubtype = {article} } We observe the quantum Zeno effect—where the act of measurement slows the rate of quantum state transitions—in a superconducting qubit using linear circuit quantum electrodynamics readout and a near-quantum-limited following amplifier. Under simultaneous strong measurement and qubit drive, the qubit undergoes a series of quantum jumps between states. These jumps are visible in the experimental measurement record and are analyzed using maximum likelihood estimation to determine qubit transition rates. The observed rates agree with both analytical predictions and numerical simulations. The analysis methods are suitable for processing general noisy random telegraph signals. |
Chantasri, A., Schwartz, M. E., Roch, N., Siddiqi, I., Jordan, A. N. Quantum trajectories and their statistics for remotely entangled quantum bits (Journal Article) ArXiv e-prints, 2016. (Links | BibTeX | Tags: Quantum Physics, Quantum Trajectories, Superconducting Qubits) @article{2016arXiv160309623Cb, title = {Quantum trajectories and their statistics for remotely entangled quantum bits}, author = {Chantasri, A. and Schwartz, M. E. and Roch, N. and Siddiqi, I. and Jordan, A. N.}, url = {http://arxiv.org/abs/1603.09623v1}, year = {2016}, date = {2016-03-31}, journal = {ArXiv e-prints}, keywords = {Quantum Physics, Quantum Trajectories, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Toyli, D. M., Eddins, A. W., Boutin, S., Puri, S., Hover, D., Bolkhovsky, V., Oliver, W. D., Siddiqi, I. Resonance fluorescence from an artificial atom in squeezed vacuum (Journal Article) Phys. Rev. X 6, 031004 (2016), 2016, (Viewpoint by Howard J. Carmichael: http://physics.aps.org/articles/v9/77). (Abstract | Links | BibTeX | Tags: squeezed, Superconducting Qubits) @article{Toyli2016, title = {Resonance fluorescence from an artificial atom in squeezed vacuum}, author = {Toyli, D. M. and Eddins, A. W. and Boutin, S. and Puri, S. and Hover, D. and Bolkhovsky, V. and Oliver, W. D. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevX.6.031004 http://arxiv.org/abs/1602.03240 }, year = {2016}, date = {2016-02-10}, journal = {Phys. Rev. X 6, 031004 (2016)}, abstract = {We present an experimental realization of resonance fluorescence in squeezed vacuum. We strongly couple microwave-frequency squeezed light to a superconducting artificial atom and detect the resulting fluorescence with high resolution enabled by a broadband traveling-wave parametric amplifier. We investigate the fluorescence spectra in the weak and strong driving regimes, observing up to 3.1 dB of reduction of the fluorescence linewidth below the ordinary vacuum level and a dramatic dependence of the Mollow triplet spectrum on the relative phase of the driving and squeezed vacuum fields. Our results are in excellent agreement with predictions for spectra produced by a two-level atom in squeezed vacuum [Phys. Rev. Lett. 58, 2539 (1987)], demonstrating that resonance fluorescence offers a resource-efficient means to characterize squeezing in cryogenic environments.}, note = {Viewpoint by Howard J. Carmichael: http://physics.aps.org/articles/v9/77}, keywords = {squeezed, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } We present an experimental realization of resonance fluorescence in squeezed vacuum. We strongly couple microwave-frequency squeezed light to a superconducting artificial atom and detect the resulting fluorescence with high resolution enabled by a broadband traveling-wave parametric amplifier. We investigate the fluorescence spectra in the weak and strong driving regimes, observing up to 3.1 dB of reduction of the fluorescence linewidth below the ordinary vacuum level and a dramatic dependence of the Mollow triplet spectrum on the relative phase of the driving and squeezed vacuum fields. Our results are in excellent agreement with predictions for spectra produced by a two-level atom in squeezed vacuum [Phys. Rev. Lett. 58, 2539 (1987)], demonstrating that resonance fluorescence offers a resource-efficient means to characterize squeezing in cryogenic environments. |
2015 |
Hacohen-Gourgy, S., Ramasesh, V. V., De Grandi, C., Siddiqi, I., Girvin, S. M. Cooling and Autonomous Feedback in a Bose-Hubbard Chain with Attractive Interactions (Journal Article) Phys. Rev. Lett., 115 , pp. 240501, 2015. (Links | BibTeX | Tags: Bath Engineering, Superconducting Qubits) @article{PhysRevLett.115.240501, title = {Cooling and Autonomous Feedback in a Bose-Hubbard Chain with Attractive Interactions}, author = {Hacohen-Gourgy, S. and Ramasesh, V. V. and De Grandi, C. and Siddiqi, I. and Girvin, S. M.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.115.240501 http://arxiv.org/abs/1506.05837}, doi = {10.1103/PhysRevLett.115.240501}, year = {2015}, date = {2015-12-01}, journal = {Phys. Rev. Lett.}, volume = {115}, pages = {240501}, publisher = {American Physical Society}, keywords = {Bath Engineering, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Tan, D., Weber, S. J., Siddiqi, I., Mølmer, K., Murch, K. W. Prediction and Retrodiction for a Continuously Monitored Superconducting Qubit (Journal Article) Phys. Rev. Lett., 114 , pp. 090403, 2015. (Links | BibTeX | Tags: quantum feedback, Superconducting Qubits) @article{PhysRevLett.114.090403, title = {Prediction and Retrodiction for a Continuously Monitored Superconducting Qubit}, author = {Tan, D. and Weber, S. J. and Siddiqi, I. and M{\o}lmer, K. and Murch, K. W.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.114.090403 http://arxiv.org/abs/1409.0510}, doi = {10.1103/PhysRevLett.114.090403}, year = {2015}, date = {2015-03-01}, journal = {Phys. Rev. Lett.}, volume = {114}, pages = {090403}, publisher = {American Physical Society}, keywords = {quantum feedback, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Macklin, C., O'Brien, K., Hover, D., Schwartz, M. E., Bolkhovsky, V., Zhang, X., Oliver, W. D., Siddiqi, I. A near–quantum-limited Josephson traveling-wave parametric amplifier (Journal Article) Science, 350 (6258), pp. 307–310, 2015, ISSN: 0036-8075. (Abstract | Links | BibTeX | Tags: Novel Josephson Device, Parametric Amplifier, Traveling Wave Parametric Amplifiers) @article{Macklin307, title = {A near{\textendash}quantum-limited Josephson traveling-wave parametric amplifier}, author = {Macklin, C. and O'Brien, K. and Hover, D. and Schwartz, M. E. and Bolkhovsky, V. and Zhang, X. and Oliver, W. D. and Siddiqi, I.}, url = {http://science.sciencemag.org/content/350/6258/307}, doi = {10.1126/science.aaa8525}, issn = {0036-8075}, year = {2015}, date = {2015-01-01}, journal = {Science}, volume = {350}, number = {6258}, pages = {307--310}, publisher = {American Association for the Advancement of Science}, abstract = {Amplifying microwave signals with high gain and across a broad range of frequencies is crucial in solid-state quantum information processing (QIP). Achieving broadband operation is especially tricky. Macklin et al. engineered an amplifier that contains a long chain of so-called Josephson junctions (see the Perspective by Cleland). The amplifier exhibited high gain over a gigahertz-sized bandwidth and was able to perform high-fidelity qubit readout. Because the amplifier will be capable of reading out as many as 20 qubits simultaneously, it may help to scale up QIP protocols.Science, this issue p. 307; see also p. 280Detecting single{\textendash}photon level signals{\textemdash}carriers of both classical and quantum information{\textemdash}is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics.}, keywords = {Novel Josephson Device, Parametric Amplifier, Traveling Wave Parametric Amplifiers}, pubstate = {published}, tppubtype = {article} } Amplifying microwave signals with high gain and across a broad range of frequencies is crucial in solid-state quantum information processing (QIP). Achieving broadband operation is especially tricky. Macklin et al. engineered an amplifier that contains a long chain of so-called Josephson junctions (see the Perspective by Cleland). The amplifier exhibited high gain over a gigahertz-sized bandwidth and was able to perform high-fidelity qubit readout. Because the amplifier will be capable of reading out as many as 20 qubits simultaneously, it may help to scale up QIP protocols.Science, this issue p. 307; see also p. 280Detecting single–photon level signals—carriers of both classical and quantum information—is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics. |
2014 |
O'Brien, K., Macklin, C., Siddiqi, I., Zhang, X. Resonant Phase Matching of Josephson Junction Traveling Wave Parametric Amplifiers (Journal Article) Phys. Rev. Lett., 113 , pp. 157001, 2014. (Links | BibTeX | Tags: Parametric Amplifier, Traveling Wave Parametric Amplifiers) @article{PhysRevLett.113.157001, title = {Resonant Phase Matching of Josephson Junction Traveling Wave Parametric Amplifiers}, author = {O'Brien, K. and Macklin, C. and Siddiqi, I. and Zhang, X.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.113.157001 http://arxiv.org/abs/1406.2346}, doi = {10.1103/PhysRevLett.113.157001}, year = {2014}, date = {2014-10-01}, journal = {Phys. Rev. Lett.}, volume = {113}, pages = {157001}, publisher = {American Physical Society}, keywords = {Parametric Amplifier, Traveling Wave Parametric Amplifiers}, pubstate = {published}, tppubtype = {article} } |
Roch, N., Schwartz, M. E., Motzoi, F., Macklin, C., Vijay, R., Eddins, A. W., Korotkov, A. N., Whaley, K. B., Sarovar, M., Siddiqi, I. Observation of Measurement-Induced Entanglement and Quantum Trajectories of Remote Superconducting Qubits (Journal Article) Phys. Rev. Lett., 112 , pp. 170501, 2014. (Links | BibTeX | Tags: Quantum Trajectories) @article{PhysRevLett.112.170501, title = {Observation of Measurement-Induced Entanglement and Quantum Trajectories of Remote Superconducting Qubits}, author = {Roch, N. and Schwartz, M. E. and Motzoi, F. and Macklin, C. and Vijay, R. and Eddins, A. W. and Korotkov, A. N. and Whaley, K. B. and Sarovar, M. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.112.170501 http://arxiv.org/abs/1402.1868}, doi = {10.1103/PhysRevLett.112.170501}, year = {2014}, date = {2014-04-01}, journal = {Phys. Rev. Lett.}, volume = {112}, pages = {170501}, publisher = {American Physical Society}, keywords = {Quantum Trajectories}, pubstate = {published}, tppubtype = {article} } |
Weber, S. J., Chantasri, A., Dressel, J., Jordan, A. N., Murch, K. W., Siddiqi, I. Mapping the optimal route between two quantum states (Journal Article) Nature, 511 (7511), pp. 570–573, 2014. (Links | BibTeX | Tags: Quantum Trajectories) @article{weber2014mapping, title = {Mapping the optimal route between two quantum states}, author = {Weber, S. J. and Chantasri, A. and Dressel, J. and Jordan, A. N. and Murch, K. W. and Siddiqi, I. }, url = {http://www.nature.com/nature/journal/v511/n7511/abs/nature13559.html http://arxiv.org/abs/1403.4992}, year = {2014}, date = {2014-01-01}, journal = {Nature}, volume = {511}, number = {7511}, pages = {570--573}, publisher = {Nature Publishing Group}, keywords = {Quantum Trajectories}, pubstate = {published}, tppubtype = {article} } |
Levenson-Falk, E. M., Kos, F., Vijay, R., Glazman, L., Siddiqi, I. Single-Quasiparticle Trapping in Aluminum Nanobridge Josephson Junctions (Journal Article) Phys. Rev. Lett., 112 , pp. 047002, 2014. (Links | BibTeX | Tags: Josephson Junctions) @article{PhysRevLett.112.047002, title = {Single-Quasiparticle Trapping in Aluminum Nanobridge Josephson Junctions}, author = {Levenson-Falk, E. M. and Kos, F. and Vijay, R. and Glazman, L. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.112.047002 http://arxiv.org/abs/1310.6996}, doi = {10.1103/PhysRevLett.112.047002}, year = {2014}, date = {2014-01-01}, journal = {Phys. Rev. Lett.}, volume = {112}, pages = {047002}, publisher = {American Physical Society}, keywords = {Josephson Junctions}, pubstate = {published}, tppubtype = {article} } |
Rao, S. G, Karim, A.and Schwartz, J., Antler, N., S., T., Siddiqi, I. Directed Assembly of Nanodiamond Nitrogen-Vacancy Centers on a Chemically Modified Patterned Surface (Journal Article) ACS applied materials & interfaces, 6 (15), pp. 12893–12900, 2014. @article{rao2014directed, title = {Directed Assembly of Nanodiamond Nitrogen-Vacancy Centers on a Chemically Modified Patterned Surface}, author = {Rao, S. G and Karim, A.and Schwartz, J. and Antler, N. and S., T. and Siddiqi, I.}, url = {http://pubs.acs.org/doi/abs/10.1021/am5027665}, year = {2014}, date = {2014-01-01}, journal = {ACS applied materials & interfaces}, volume = {6}, number = {15}, pages = {12893--12900}, publisher = {ACS Publications}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Schmidt, A. R., Henry, E., Lo, C. C., Wang, Y.-T., Li, H., Greenman, L., Namaan, O., Schenkel, T., Whaley, K. B., Bokor, J., Yablonovitch, E., Siddiqi, I. A prototype silicon double quantum dot with dispersive microwave readout (Journal Article) Journal of Applied Physics, 116 (4), pp. -, 2014. (Links | BibTeX | Tags: dispersive measurement) @article{:/content/aip/journal/jap/116/4/10.1063/1.4890835, title = {A prototype silicon double quantum dot with dispersive microwave readout}, author = {Schmidt, A. R. and Henry, E. and Lo, C. C. and Wang, Y.-T. and Li, H. and Greenman, L. and Namaan, O. and Schenkel, T. and Whaley, K. B. and Bokor, J. and Yablonovitch, E. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/jap/116/4/10.1063/1.4890835}, doi = {http://dx.doi.org/10.1063/1.4890835}, year = {2014}, date = {2014-01-01}, journal = {Journal of Applied Physics}, volume = {116}, number = {4}, pages = {-}, keywords = {dispersive measurement}, pubstate = {published}, tppubtype = {article} } |
Khan, S., Vijay, R., Siddiqi, I., Clerk A. A. Large gain quantum-limited qubit measurement using a two-mode nonlinear cavity (Journal Article) New Journal of Physics, 16 (11), pp. 113032, 2014. (Abstract | Links | BibTeX | Tags: Cavity) @article{1367-2630-16-11-113032, title = {Large gain quantum-limited qubit measurement using a two-mode nonlinear cavity}, author = {Khan, S. and Vijay, R. and Siddiqi, I. and Clerk A. A.}, url = {http://stacks.iop.org/1367-2630/16/i=11/a=113032}, year = {2014}, date = {2014-01-01}, journal = {New Journal of Physics}, volume = {16}, number = {11}, pages = {113032}, abstract = {We provide a thorough theoretical analysis of qubit state measurement in a setup where a driven, parametrically-coupled cavity system is directly coupled to the qubit, with one of the cavities having a weak Kerr nonlinearity. Such a system could be readily realized using circuit QED architectures. We demonstrate that this setup is capable in the standard linear-response regime of both producing a highly amplified output signal while at the same time achieving near quantum-limited performance: the measurement backaction on the qubit is near the minimal amount required by the uncertainty principle. This setup thus represents a promising route for performing efficient large-gain qubit measurement that is completely on-chip, and that does not rely on the use of circulators or complex non-reciprocal amplifiers.}, keywords = {Cavity}, pubstate = {published}, tppubtype = {article} } We provide a thorough theoretical analysis of qubit state measurement in a setup where a driven, parametrically-coupled cavity system is directly coupled to the qubit, with one of the cavities having a weak Kerr nonlinearity. Such a system could be readily realized using circuit QED architectures. We demonstrate that this setup is capable in the standard linear-response regime of both producing a highly amplified output signal while at the same time achieving near quantum-limited performance: the measurement backaction on the qubit is near the minimal amount required by the uncertainty principle. This setup thus represents a promising route for performing efficient large-gain qubit measurement that is completely on-chip, and that does not rely on the use of circulators or complex non-reciprocal amplifiers. |
2013 |
Yaakobi, O., Friedland, L., Macklin, C., Siddiqi, I. Parametric amplification in Josephson junction embedded transmission lines (Journal Article) Phys. Rev. B, 87 , pp. 144301, 2013. (Links | BibTeX | Tags: Josephson Junctions, Parametric Amplifier) @article{PhysRevB.87.144301, title = {Parametric amplification in Josephson junction embedded transmission lines}, author = {Yaakobi, O. and Friedland, L. and Macklin, C. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevB.87.144301}, doi = {10.1103/PhysRevB.87.144301}, year = {2013}, date = {2013-04-01}, journal = {Phys. Rev. B}, volume = {87}, pages = {144301}, publisher = {American Physical Society}, keywords = {Josephson Junctions, Parametric Amplifier}, pubstate = {published}, tppubtype = {article} } |
Murch, K. W., Weber, S. J., Macklin, C., Siddiqi, I. Observing single quantum trajectories of a superconducting quantum bit (Journal Article) Nature, 502 (7470), pp. 211–214, 2013. (Links | BibTeX | Tags: Quantum Trajectories, Superconducting Qubits) @article{murch2013observing, title = {Observing single quantum trajectories of a superconducting quantum bit}, author = {Murch, K. W. and Weber, S. J. and Macklin, C. and Siddiqi, I.}, url = {http://arxiv.org/abs/1305.7270 http://www.nature.com/nature/journal/v502/n7470/full/nature12539.html}, year = {2013}, date = {2013-01-01}, journal = {Nature}, volume = {502}, number = {7470}, pages = {211--214}, publisher = {Nature Publishing Group}, keywords = {Quantum Trajectories, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Murch, K. W., Weber, S. J., Beck, K. M., Ginossar, Eran., Siddiqi, I. Reduction of the radiative decay of atomic coherence in squeezed vacuum (Journal Article) Nature, 499 (7456), pp. 62–65, 2013. (Links | BibTeX | Tags: coherence, squeezed, Superconducting Qubits) @article{murch2013reduction, title = {Reduction of the radiative decay of atomic coherence in squeezed vacuum}, author = {Murch, K. W. and Weber, S. J. and Beck, K. M. and Ginossar, Eran. and Siddiqi, I.}, url = {http://www.nature.com/nature/journal/v499/n7456/full/nature12264.html http://arxiv.org/abs/1301.6276}, year = {2013}, date = {2013-01-01}, journal = {Nature}, volume = {499}, number = {7456}, pages = {62--65}, publisher = {Nature Publishing Group}, keywords = {coherence, squeezed, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Levenson-Falk, E. M., Vijay, R., Antler, N., Siddiqi, I. A dispersive nanoSQUID magnetometer for ultra-low noise, high bandwidth flux detection (Journal Article) Superconductor Science and Technology, 26 (5), pp. 055015, 2013. (Links | BibTeX | Tags: magnetometer, SQUID) @article{levenson2013dispersive, title = {A dispersive nanoSQUID magnetometer for ultra-low noise, high bandwidth flux detection}, author = {Levenson-Falk, E. M. and Vijay, R. and Antler, N. and Siddiqi, I.}, url = {http://iopscience.iop.org/0953-2048/26/5/055015/ http://arxiv.org/abs/1301.3184}, year = {2013}, date = {2013-01-01}, journal = {Superconductor Science and Technology}, volume = {26}, number = {5}, pages = {055015}, publisher = {IOP Publishing}, keywords = {magnetometer, SQUID}, pubstate = {published}, tppubtype = {article} } |
Antler, N., Levenson-Falk, E. M., Naik, R., Sun, Y.-D., Narla, A., Vijay, R., Siddiqi, I. In-plane magnetic field tolerance of a dispersive aluminum nanobridge SQUID magnetometer (Journal Article) Applied Physics Letters, 102 (23), pp. -, 2013. (Links | BibTeX | Tags: magnetometer, SQUID) @article{:/content/aip/journal/apl/102/23/10.1063/1.4809782, title = {In-plane magnetic field tolerance of a dispersive aluminum nanobridge SQUID magnetometer}, author = {Antler, N. and Levenson-Falk, E. M. and Naik, R. and Sun, Y.-D. and Narla, A. and Vijay, R. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/apl/102/23/10.1063/1.4809782 http://arxiv.org/abs/1303.2737}, doi = {http://dx.doi.org/10.1063/1.4809782}, year = {2013}, date = {2013-01-01}, journal = {Applied Physics Letters}, volume = {102}, number = {23}, pages = {-}, keywords = {magnetometer, SQUID}, pubstate = {published}, tppubtype = {article} } |
2012 |
Murch, K. W., Ginossar, E., Weber, S. J., Vijay, R., Girvin, S. M., Siddiqi, I. Quantum state sensitivity of an autoresonant superconducting circuit (Journal Article) Phys. Rev. B, 86 , pp. 220503, 2012. (Links | BibTeX | Tags: Superconducting Qubits) @article{PhysRevB.86.220503, title = {Quantum state sensitivity of an autoresonant superconducting circuit}, author = {Murch, K. W. and Ginossar, E. and Weber, S. J. and Vijay, R. and Girvin, S. M. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevB.86.220503 http://lanl.arxiv.org/abs/1208.4646}, doi = {10.1103/PhysRevB.86.220503}, year = {2012}, date = {2012-12-01}, journal = {Phys. Rev. B}, volume = {86}, pages = {220503}, publisher = {American Physical Society}, keywords = {Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Murch, K. W., Vool, U., Zhou, D., Weber, S. J., Girvin, S. M., Siddiqi, I. Cavity-Assisted Quantum Bath Engineering (Journal Article) Phys. Rev. Lett., 109 , pp. 183602, 2012. (Links | BibTeX | Tags: Bath Engineering, Superconducting Qubits) @article{PhysRevLett.109.183602, title = {Cavity-Assisted Quantum Bath Engineering}, author = {Murch, K. W. and Vool, U. and Zhou, D. and Weber, S. J. and Girvin, S. M. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.109.183602 http://arxiv.org/abs/1207.0053}, doi = {10.1103/PhysRevLett.109.183602}, year = {2012}, date = {2012-10-01}, journal = {Phys. Rev. Lett.}, volume = {109}, pages = {183602}, publisher = {American Physical Society}, keywords = {Bath Engineering, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Slichter, D. H., Vijay, R., Weber, S. J., Boutin, S., Boissonneault, M., Gambetta, J. M., Blais, A., Siddiqi, I. Measurement-Induced Qubit State Mixing in Circuit QED from Up-Converted Dephasing Noise (Journal Article) Phys. Rev. Lett., 109 , pp. 153601, 2012. (Links | BibTeX | Tags: Superconducting Qubits) @article{PhysRevLett.109.153601, title = {Measurement-Induced Qubit State Mixing in Circuit QED from Up-Converted Dephasing Noise}, author = {Slichter, D. H. and Vijay, R. and Weber, S. J. and Boutin, S. and Boissonneault, M. and Gambetta, J. M. and Blais, A. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.109.153601 http://arxiv.org/abs/1206.6946}, doi = {10.1103/PhysRevLett.109.153601}, year = {2012}, date = {2012-10-01}, journal = {Phys. Rev. Lett.}, volume = {109}, pages = {153601}, publisher = {American Physical Society}, keywords = {Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Johnson, J. E., Macklin, C., Slichter, D. H., Vijay, R., Weingarten, E. B., Clarke, John, Siddiqi, I. Heralded State Preparation in a Superconducting Qubit (Journal Article) Phys. Rev. Lett., 109 , pp. 050506, 2012. (Links | BibTeX | Tags: Superconducting Qubits) @article{PhysRevLett.109.050506, title = {Heralded State Preparation in a Superconducting Qubit}, author = {Johnson, J. E. and Macklin, C. and Slichter, D. H. and Vijay, R. and Weingarten, E. B. and Clarke, John and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.109.050506 http://arxiv.org/abs/1202.5541}, doi = {10.1103/PhysRevLett.109.050506}, year = {2012}, date = {2012-08-01}, journal = {Phys. Rev. Lett.}, volume = {109}, pages = {050506}, publisher = {American Physical Society}, keywords = {Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Murch, K. W., Weber, S. J., Levenson-Falk, E. M., Vijay, R., Siddiqi, I. 1/f noise of Josephson-junction-embedded microwave resonators at single photon energies and millikelvin temperatures (Journal Article) Applied Physics Letters, 100 (14), pp. -, 2012. (Links | BibTeX | Tags: Josephson Junctions, Resonators, Superconducting Qubits) @article{:/content/aip/journal/apl/100/14/10.1063/1.3700964, title = {1/f noise of Josephson-junction-embedded microwave resonators at single photon energies and millikelvin temperatures}, author = {Murch, K. W. and Weber, S. J. and Levenson-Falk, E. M. and Vijay, R. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/apl/100/14/10.1063/1.3700964 http://arxiv.org/abs/1112.3584}, doi = {http://dx.doi.org/10.1063/1.3700964}, year = {2012}, date = {2012-01-01}, journal = {Applied Physics Letters}, volume = {100}, number = {14}, pages = {-}, keywords = {Josephson Junctions, Resonators, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Vijay, R., Macklin, C., Slichter, D. H., Weber, S. J., Murch, K. W., Naik, R., Korotkov, A. N., Siddiqi, I. Stabilizing Rabi oscillations in a superconducting qubit using quantum feedback (Journal Article) Nature, 490 (7418), pp. 77–80, 2012. (Links | BibTeX | Tags: quantum feedback, Superconducting Qubits) @article{vijay2012stabilizing, title = {Stabilizing Rabi oscillations in a superconducting qubit using quantum feedback}, author = {Vijay, R. and Macklin, C. and Slichter, D. H. and Weber, S. J. and Murch, K. W. and Naik, R. and Korotkov, A. N. and Siddiqi, I.}, url = {http://www.nature.com/nature/journal/v490/n7418/full/nature11505.html http://arxiv.org/abs/1205.5591}, year = {2012}, date = {2012-01-01}, journal = {Nature}, volume = {490}, number = {7418}, pages = {77--80}, publisher = {Nature Publishing Group}, keywords = {quantum feedback, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
2011 |
Johnson, J. E., Hoskinson, E. M., Macklin, C., Slichter, D. H., Siddiqi, I., Clarke, John Dispersive readout of a flux qubit at the single-photon level (Journal Article) Phys. Rev. B, 84 , pp. 220503, 2011. (Links | BibTeX | Tags: dispersive measurement, Superconducting Qubits) @article{PhysRevB.84.220503, title = {Dispersive readout of a flux qubit at the single-photon level}, author = {Johnson, J. E. and Hoskinson, E. M. and Macklin, C. and Slichter, D. H. and Siddiqi, I. and Clarke, John}, url = {http://link.aps.org/doi/10.1103/PhysRevB.84.220503 http://arxiv.org/abs/1109.2858}, doi = {10.1103/PhysRevB.84.220503}, year = {2011}, date = {2011-12-01}, journal = {Phys. Rev. B}, volume = {84}, pages = {220503}, publisher = {American Physical Society}, keywords = {dispersive measurement, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Hatridge, M., Vijay, R., Slichter, D. H., Clarke, John, Siddiqi, I. Dispersive magnetometry with a quantum limited SQUID parametric amplifier (Journal Article) Phys. Rev. B, 83 , pp. 134501, 2011. (Links | BibTeX | Tags: magnetometer, Parametric Amplifier, SQUID) @article{PhysRevB.83.134501, title = {Dispersive magnetometry with a quantum limited SQUID parametric amplifier}, author = {Hatridge, M. and Vijay, R. and Slichter, D. H. and Clarke, John and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevB.83.134501 http://arxiv.org/abs/1003.2466}, doi = {10.1103/PhysRevB.83.134501}, year = {2011}, date = {2011-04-01}, journal = {Phys. Rev. B}, volume = {83}, pages = {134501}, publisher = {American Physical Society}, keywords = {magnetometer, Parametric Amplifier, SQUID}, pubstate = {published}, tppubtype = {article} } |
Vijay, R., Slichter, D. H., Siddiqi, I. Observation of Quantum Jumps in a Superconducting Artificial Atom (Journal Article) Phys. Rev. Lett., 106 , pp. 110502, 2011. (Links | BibTeX | Tags: quantum jump, Superconducting Qubits) @article{PhysRevLett.106.110502, title = {Observation of Quantum Jumps in a Superconducting Artificial Atom}, author = {Vijay, R. and Slichter, D. H. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.106.110502 http://arxiv.org/abs/1009.2969}, doi = {10.1103/PhysRevLett.106.110502}, year = {2011}, date = {2011-03-01}, journal = {Phys. Rev. Lett.}, volume = {106}, pages = {110502}, publisher = {American Physical Society}, keywords = {quantum jump, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Siddiqi, I. Superconducting qubits: poised for computing? (Journal Article) Superconductor Science and Technology, 24 (9), pp. 91002–91010, 2011. (Links | BibTeX | Tags: computing, Superconducting Qubits) @article{siddiqi2011superconducting, title = {Superconducting qubits: poised for computing?}, author = {Siddiqi, I.}, url = {http://iopscience.iop.org/0953-2048/24/9/091002}, year = {2011}, date = {2011-01-01}, journal = {Superconductor Science and Technology}, volume = {24}, number = {9}, pages = {91002--91010}, publisher = {IOP Publishing}, keywords = {computing, Superconducting Qubits}, pubstate = {published}, tppubtype = {article} } |
Levenson-Falk, E. M., Vijay, R., Siddiqi, I. Nonlinear microwave response of aluminum weak-link Josephson oscillators (Journal Article) Applied Physics Letters, 98 (12), pp. -, 2011. (Links | BibTeX | Tags: Josephson Junctions, Novel Josephson Device) @article{:/content/aip/journal/apl/98/12/10.1063/1.3570693, title = {Nonlinear microwave response of aluminum weak-link Josephson oscillators}, author = {Levenson-Falk, E. M. and Vijay, R. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/apl/98/12/10.1063/1.3570693 http://arxiv.org/abs/1101.4672}, doi = {http://dx.doi.org/10.1063/1.3570693}, year = {2011}, date = {2011-01-01}, journal = {Applied Physics Letters}, volume = {98}, number = {12}, pages = {-}, keywords = {Josephson Junctions, Novel Josephson Device}, pubstate = {published}, tppubtype = {article} } |
Weber, S. J., Murch, K. W., Slichter, D. H., Vijay, R., Siddiqi, I. Single crystal silicon capacitors with low microwave loss in the single photon regime (Journal Article) Applied Physics Letters, 98 (17), pp. -, 2011. (Links | BibTeX | Tags: Cryogenic Microwave Technology) @article{:/content/aip/journal/apl/98/17/10.1063/1.3583449, title = {Single crystal silicon capacitors with low microwave loss in the single photon regime}, author = {Weber, S. J. and Murch, K. W. and Slichter, D. H. and Vijay, R. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/apl/98/17/10.1063/1.3583449 http://arxiv.org/abs/1102.2917}, doi = {http://dx.doi.org/10.1063/1.3583449}, year = {2011}, date = {2011-01-01}, journal = {Applied Physics Letters}, volume = {98}, number = {17}, pages = {-}, keywords = {Cryogenic Microwave Technology}, pubstate = {published}, tppubtype = {article} } |
2010 |
Vijay, R., Levenson-Falk, E. M., Slichter, D. H., Siddiqi, I. Approaching ideal weak link behavior with three dimensional aluminum nanobridges (Journal Article) Applied Physics Letters, 96 (22), pp. -, 2010. (Links | BibTeX | Tags: Novel Josephson Device) @article{:/content/aip/journal/apl/96/22/10.1063/1.3443716, title = {Approaching ideal weak link behavior with three dimensional aluminum nanobridges}, author = {Vijay, R. and Levenson-Falk, E. M. and Slichter, D. H. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/apl/96/22/10.1063/1.3443716 http://arxiv.org/abs/1005.1110}, doi = {http://dx.doi.org/10.1063/1.3443716}, year = {2010}, date = {2010-01-01}, journal = {Applied Physics Letters}, volume = {96}, number = {22}, pages = {-}, keywords = {Novel Josephson Device}, pubstate = {published}, tppubtype = {article} } |
2009 |
Vijay, R., Sau, J. D., Cohen, Marvin L., Siddiqi, I. Optimizing Anharmonicity in Nanoscale Weak Link Josephson Junction Oscillators (Journal Article) Phys. Rev. Lett., 103 , pp. 087003, 2009. (Links | BibTeX | Tags: Josephson Junctions, Novel Josephson Device) @article{PhysRevLett.103.087003, title = {Optimizing Anharmonicity in Nanoscale Weak Link Josephson Junction Oscillators}, author = {Vijay, R. and Sau, J. D. and Cohen, Marvin L. and Siddiqi, I.}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.103.087003 http://arxiv.org/abs/0905.2217}, doi = {10.1103/PhysRevLett.103.087003}, year = {2009}, date = {2009-08-01}, journal = {Phys. Rev. Lett.}, volume = {103}, pages = {087003}, publisher = {American Physical Society}, keywords = {Josephson Junctions, Novel Josephson Device}, pubstate = {published}, tppubtype = {article} } |
Vijay, R., Devoret, M. H., Siddiqi, I. Invited Review Article: The Josephson bifurcation amplifier (Journal Article) Review of Scientific Instruments, 80 (11), pp. -, 2009. (Links | BibTeX | Tags: Josephson Junctions, Parametric Amplifier) @article{:/content/aip/journal/rsi/80/11/10.1063/1.3224703, title = {Invited Review Article: The Josephson bifurcation amplifier}, author = {Vijay, R. and Devoret, M. H. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/rsi/80/11/10.1063/1.3224703}, doi = {http://dx.doi.org/10.1063/1.3224703}, year = {2009}, date = {2009-01-01}, journal = {Review of Scientific Instruments}, volume = {80}, number = {11}, pages = {-}, keywords = {Josephson Junctions, Parametric Amplifier}, pubstate = {published}, tppubtype = {article} } |
Slichter, D. H., Naaman, O., Siddiqi, I. Millikelvin thermal and electrical performance of lossy transmission line filters (Journal Article) Applied Physics Letters, 94 (19), pp. -, 2009. (Links | BibTeX | Tags: Cryogenic Microwave Technology) @article{:/content/aip/journal/apl/94/19/10.1063/1.3133362, title = {Millikelvin thermal and electrical performance of lossy transmission line filters}, author = {Slichter, D. H. and Naaman, O. and Siddiqi, I.}, url = {http://scitation.aip.org/content/aip/journal/apl/94/19/10.1063/1.3133362 http://arxiv.org/abs/0903.1895}, doi = {http://dx.doi.org/10.1063/1.3133362}, year = {2009}, date = {2009-01-01}, journal = {Applied Physics Letters}, volume = {94}, number = {19}, pages = {-}, keywords = {Cryogenic Microwave Technology}, pubstate = {published}, tppubtype = {article} } |
