Benchmarking Coherent Errors in Controlled-Phase Gates due to Spectator Qubits

Krinner, Sebastian; Lazar, Stefania; Remm, Ants; Andersen, Christian Kraglund; Lacroix, Nathan; Norris, Graham J.; Hellings, Christoph; Gabureac, Mihai; Eichler, Christopher; Wallraff, Andreas

doi:10.1103/physrevapplied.14.024042

Cited by 66 publications

(52 citation statements)

References 52 publications

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“…Errors due to decoherence mostly affect the contrast of the landscapes [37], see Fig. 3(c) and Appendix G. The distortions of the local extrema located at γ > π/2 are attributed to the residual ZZ coupling between the qubits [38], which we confirm with master-equation simulations, see Appendix G.…”

Section: Performance Of Qaoasupporting

confidence: 80%

“…The acquired conditional phase φ is determined relative to a measurement without applying π pulses to the higher-frequency qubit. The conditional phase results from the total ZZ interaction, which naturally includes residual ZZ coupling for the duration of the gate [38].…”

Section: Appendix B: Controlled Arbitrary Phase Gatementioning

confidence: 99%

“…In addition to the incoherent errors introduced by the Lindblad terms, it is important to also consider the impact of coherent errors on the algorithm. In our experiment, the main source of coherent errors is residual ZZ coupling between neighboring qubits [38]. To model this coupling in the numerical simulations, we include the Hamiltonian…”

Section: Appendix G: Master-equation Simulationsmentioning

confidence: 99%

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Improving the Performance of Deep Quantum Optimization Algorithms with Continuous Gate Sets

et al. 2020

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Variational quantum algorithms are believed to be promising for solving computationally hard problems on noisy intermediate-scale quantum (NISQ) systems. Gaining computational power from these algorithms critically relies on the mitigation of errors during their execution, which for coherence-limited operations is achievable by reducing the gate count. Here, we demonstrate an improvement of up to a factor of 3 in algorithmic performance for the quantum approximate optimization algorithm (QAOA) as measured by the success probability, by implementing a continuous hardware-efficient gate set using superconducting quantum circuits. This gate set allows us to perform the phase separation step in QAOA with a single physical gate for each pair of qubits instead of decomposing it into two CZ gates and single-qubit gates. With this reduced number of physical gates, which scales with the number of layers employed in the algorithm, we experimentally investigate the circuit-depth-dependent performance of QAOA applied to exact-cover problem instances mapped onto three and seven qubits, using up to a total of 399 operations and up to nine layers. Our results demonstrate that the use of continuous gate sets may be a key component in extending the impact of near-term quantum computers.

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Section: Performance Of Qaoasupporting

confidence: 80%

Section: Appendix B: Controlled Arbitrary Phase Gatementioning

confidence: 99%

Section: Appendix G: Master-equation Simulationsmentioning

confidence: 99%

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Improving the Performance of Deep Quantum Optimization Algorithms with Continuous Gate Sets

et al. 2020

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“…However, due to crosstalk, an operation on target qubit(s) may impact the non-target qubit(s). Several protocols have been presented in [2]- [11] to detect and benchmark crosstalk in Quantum Computers (QC). However, use-case of crosstalk in noisy quantum circuit simulation is not well explored with experimental error rates similar to gate errors.…”

Section: Introductionmentioning

confidence: 99%

Experimental Characterization, Modeling, and Analysis of Crosstalk in a Quantum Computer

Saki

Alam

Ghosh

2020

IEEE Trans. Quantum Eng.

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In this article, we present the experimental characterization of crosstalk in quantum information processor using idle tomography and simultaneous randomized benchmarking. We quantify both "quantum" and "classical" crosstalk in the device and analyze quantum circuits considering crosstalk. We show that simulation considering only gate-error deviates from experimental results up to 27%, whereas simulation considering both gate error and crosstalk match the experiments more accurately with an average mismatch as low as 4.52%. This article enables simulation of quantum circuits with experimental crosstalk error rates.INDEX TERMS Crosstalk, idle tomography, simultaneous randomized benchmarking, zz-interaction.

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“…To reduce leakage from linear-dynamical distortion in flux-control lines and limited time resolution in arbitrary waveform generators (AWGs), unipolar square pulses [8,18] have been superseded by softened counterparts [19,20] based on fast-adiabatic theory [21]. In parallel, coupling strengths have reduced to J 2 =2π ∼ 10-20 MHz to mitigate residual ZZ coupling, which affects single-qubit gates and idling at bias points, and produces crosstalk from spectator qubits [22]. Many groups are actively developing tunable coupling schemes to suppress residual coupling without incurring slowdown [23][24][25][26][27].…”

mentioning

confidence: 99%

High-Fidelity Controlled- Z Gate with Maximal Intermediate Leakage Operating at the Speed Limit in a Superconducting Quantum Processor

et al. 2021

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Simple tuneup of fast two-qubit gates is essential for the scaling of quantum processors. We introduce the sudden variant (SNZ) of the net zero scheme realizing controlled-Z (CZ) gates by flux control of transmon frequency. SNZ CZ gates realized in a multitransmon processor operate at the speed limit of transverse coupling between computational and noncomputational states by maximizing intermediate leakage. Beyond speed, the key advantage of SNZ is tuneup simplicity, owing to the regular structure of conditional phase and leakage as a function of two control parameters. SNZ is compatible with scalable schemes for quantum error correction and adaptable to generalized conditional-phase gates useful in intermediate-scale applications.

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Benchmarking Coherent Errors in Controlled-Phase Gates due to Spectator Qubits

Cited by 66 publications

References 52 publications

Improving the Performance of Deep Quantum Optimization Algorithms with Continuous Gate Sets

Improving the Performance of Deep Quantum Optimization Algorithms with Continuous Gate Sets

Experimental Characterization, Modeling, and Analysis of Crosstalk in a Quantum Computer

High-Fidelity Controlled- Z Gate with Maximal Intermediate Leakage Operating at the Speed Limit in a Superconducting Quantum Processor

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