Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

Ficheux, Quentin; Jezouin, Sébastien; Leghtas, Zaki; Huard, Benjamin

doi:10.1038/s41467-018-04372-9

Cited by 80 publications

(78 citation statements)

References 40 publications

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“…The sample measured in this work is the same one as in [36]. The transmon is made of a single aluminum Josephson junction and is embedded in a copper cavity of 26.5 × 26.5 × 9.5 mm 3 thermalized on the base plate of a dilution fridge at about 10 mK.…”

Section: A Sample Fabricationmentioning

confidence: 99%

Escape of a Driven Quantum Josephson Circuit into Unconfined States

et al. 2019

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Josephson circuits have been ideal systems to study complex non-linear dynamics which can lead to chaotic behavior and instabilities. More recently, Josephson circuits in the quantum regime, particularly in the presence of microwave drives, have demonstrated their ability to emulate a variety of Hamiltonians that are useful for the processing of quantum information. In this paper we show that these drives lead to an instability which results in the escape of the circuit mode into states that are not confined by the Josephson cosine potential. We observe this escape in a ubiquitous circuit: a transmon embedded in a 3D cavity. When the transmon occupies these free-particle-like states, the circuit behaves as though the junction had been removed, and all non-linearities are lost. This work deepens our understanding of strongly driven Josephson circuits, which is important for fundamental and application perspectives, such as the engineering of Hamiltonians by parametric pumping.

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Section: A Sample Fabricationmentioning

confidence: 99%

Escape of a Driven Quantum Josephson Circuit into Unconfined States

et al. 2019

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“…Maximizing this efficiency for superconducting qubit measurements requires multiple stages of cyrogenic amplification to boost information-bearing quantum microwaves above the noise floor of room-temperature electronics. The use of off-chip superconducting parametric amplifiers for the first gain stage has enabled a variety of experiments investigating quantum measurement dynamics [1][2][3][4][5][6], with improvements in efficiency reported using multi-junction circuits [7]. However, prior to amplification the information encoded in the field is extremely fragile, such that in these configurations ∼30% of the information is dissipated in lossy microwave circulators and other components en route to the amplifier, lowering the ceiling on η meas .…”

Section: Introductionmentioning

confidence: 99%

High-Efficiency Measurement of an Artificial Atom Embedded in a Parametric Amplifier

et al. 2019

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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 a two-level artificial atom, comprised of a transmon qubit, within a flux-pumped Josephson parametric amplifier. Surprisingly, this configuration is able to enhance dispersive measurement without exposing the qubit to appreciable excess backaction. This is accomplished 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-toend 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. arXiv:1806.05276v1 [quant-ph]

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“…20, which yields an average state generation fidelity of 97% and is mainly limited by the decoherence of the ancilla qubit. The repetitive QCS with controllable parameters provides a testbed for studying reservoir engineering [6], quantum Zeno effect [7][8][9]26], quantum thermodynamics [27,28], and quantum metrology [29,30]. Together with the recently demonstrated arbitrary unitary control and quantum error correction [31,32] in cQED architecture, our demonstrated QCS could realize reliable universal control of open quantum system, which is significant for quantum computation [1,25] and simulation [33,34].…”

Section: Introductionmentioning

confidence: 99%

Experimental repetitive quantum channel simulation

Cai

et al. 2018

Science Bulletin

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Universal control of quantum systems is a major goal to be achieved for quantum information processing, which demands thorough understanding of fundamental quantum mechanics and promises applications of quantum technologies. So far, most studies concentrate on ideally isolated quantum systems governed by unitary evolutions, while practical quantum systems are open and described by quantum channels due to their inevitable coupling to environment. Here, we experimentally simulate arbitrary quantum channels for an open quantum system, i.e. a single photonic qubit in a superconducting quantum circuit. The arbitrary channel simulation is achieved with minimum resource of only one ancilla qubit and measurement-based adaptive control. By repetitively implementing the quantum channel simulation, we realize an arbitrary Liouvillian for a continuous evolution of an open quantum system for the first time. Our experiment provides not only a testbed for understanding quantum noise and decoherence, but also a powerful tool for full control of practical open quantum systems.arXiv:1807.07694v1 [quant-ph]

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Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

Cited by 80 publications

References 40 publications

Escape of a Driven Quantum Josephson Circuit into Unconfined States

Escape of a Driven Quantum Josephson Circuit into Unconfined States

High-Efficiency Measurement of an Artificial Atom Embedded in a Parametric Amplifier

Experimental repetitive quantum channel simulation

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