Realization of a Binary-Outcome Projection Measurement of a Three-Level Superconducting Quantum System

Jerger, Markus; Macha, P.; Hamann, Andrés Rosario; Reshitnyk, Yarema; Júlíusson, Kristinn; Fedorov, Arkady

doi:10.1103/physrevapplied.6.014014

Cited by 14 publications

(13 citation statements)

References 32 publications

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“…For detailed information on the effect of the readout pulse on the state of a qutrit state for different detunings, including a theoretical model, experimental verification and calibration procedures, see (ref. 25 ). Probing the cavity for 350 ns, we reach a single-shot contrast of ≈ 96% between and , limited primarily by thermal excitation and decay of the qutrit state during the readouts.…”

Section: Resultsmentioning

confidence: 99%

Contextuality without nonlocality in a superconducting quantum system

et al. 2016

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Classical realism demands that system properties exist independently of whether they are measured, while noncontextuality demands that the results of measurements do not depend on what other measurements are performed in conjunction with them. The Bell–Kochen–Specker theorem states that noncontextual realism cannot reproduce the measurement statistics of a single three-level quantum system (qutrit). Noncontextual realistic models may thus be tested using a single qutrit without relying on the notion of quantum entanglement in contrast to Bell inequality tests. It is challenging to refute such models experimentally, since imperfections may introduce loopholes that enable a realist interpretation. Here we use a superconducting qutrit with deterministic, binary-outcome readouts to violate a noncontextuality inequality while addressing the detection, individual-existence and compatibility loopholes. This evidence of state-dependent contextuality also demonstrates the fitness of superconducting quantum circuits for fault-tolerant quantum computation in surface-code architectures, currently the most promising route to scalable quantum computing.

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Section: Resultsmentioning

confidence: 99%

Contextuality without nonlocality in a superconducting quantum system

et al. 2016

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“…Whenever a leaked qubit is measured, it will always return eigenvalue −1. Implicitly, this assumes two-level measurements that cannot distinguish between excited states, and is also relevant to many qubit architectures [26,38]. However, while this error-model is used in simulating logical error rates, we consider an even more damaging leakage model when accounting for fault-paths to argue about effective distance.…”

Section: Leakagementioning

confidence: 99%

Handling leakage with subsystem codes

2019

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Leakage is a particularly damaging error that occurs when a qubit state falls out of its two-level computational subspace. Compared to independent depolarizing noise, leaked qubits may produce many more configurations of harmful correlated errors during error-correction. In this work, we investigate different local codes in the low-error regime of a leakage gate error model. When restricting to bare-ancilla extraction, we observe that subsystem codes are good candidates for handling leakage, as their locality can limit damaging correlated errors. As a case study, we compare subspace surface codes to the subsystem surface codes introduced by Bravyi et al. In contrast to depolarizing noise, subsystem surface codes outperform same-distance subspace surface codes below error rates as high as 7.5×10 −4 while offering better per-qubit distance protection. Furthermore, we show that at low to intermediate distances, Bacon-Shor codes offer better per-qubit error protection against leakage in an ion-trap motivated error model below error rates as high as 1.2×10 −3 . For restricted leakage models, this advantage can be extended to higher distances by relaxing to unverified two-qubit cat state extraction in the surface code. These results highlight an intrinsic benefit of subsystem code locality to error-corrective performance.

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“…Then, the resonator probes the averaged qubit state, defined by σ z , and changing the qubit state resulted in shifting the position of the resonant transmission. Alternatively, the measurements can be done with the single-shot readout [20,[40][41][42][43]. In this case, in each measurement, the resonator would see the qubit in either the ground or excited state, with σ z equal to −1 or 1, respectively [44].…”

Section: Thermometry With Pulsed Measurementsmentioning

confidence: 99%

Thermometry and Memcapacitance with a Qubit-Resonator System

Shevchenko

Karpov

2018

Phys. Rev. Applied

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We study theoretically dynamics of a driven-dissipative qubit-resonator system. Specifically, a transmon qubit is coupled to a transmission-line resonator; this system is considered to be probed via a resonator, by means of either continuous or pulsed measurements. Analytical results obtained in the semiclassical approximation are compared with calculations in the semi-quantum theory as well as with the previous experiments. We demonstrate that the temperature dependence of the resonator frequency shift can be used for the system thermometry and that the dynamics, displaying pinched-hysteretic curve, can be useful for realization of memory devices, the quantum memcapacitors.arXiv:1805.06154v1 [cond-mat.mes-hall]

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Realization of a Binary-Outcome Projection Measurement of a Three-Level Superconducting Quantum System

Cited by 14 publications

References 32 publications

Contextuality without nonlocality in a superconducting quantum system

Contextuality without nonlocality in a superconducting quantum system

Handling leakage with subsystem codes

Thermometry and Memcapacitance with a Qubit-Resonator System

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