Bootstrapping quantum process tomography via a perturbative ansatz

Govia, Luke C. G.; Ribeill, Guilhem; Ristè, Diego; Ware, Matthew; Krovi, Hari

doi:10.1038/s41467-020-14873-1

Cited by 45 publications

(31 citation statements)

References 64 publications

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“…Another open problem is to find out whether further generalizations of Quantum Overlapping Tomography can be used to perform reliable characterization of more general types of noise -coherent measurement noise and the noise affecting quantum gates. For example, in the work [66] the authors consider an ansatz for the generic noisy quantum process which uses only 2-local noise processes -a setup which seems natural to benefit from similar techniques. In Refs.…”

Section: Future Researchmentioning

confidence: 99%

Modeling and mitigation of cross-talk effects in readout noise with applications to the Quantum Approximate Optimization Algorithm

Maciejewski

Baccari

Zimborás

et al. 2021

Quantum

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Measurement noise is one of the main sources of errors in currently available quantum devices based on superconducting qubits. At the same time, the complexity of its characterization and mitigation often exhibits exponential scaling with the system size. In this work, we introduce a correlated measurement noise model that can be efficiently described and characterized, and which admits effective noise-mitigation on the level of marginal probability distributions. Noise mitigation can be performed up to some error for which we derive upper bounds. Characterization of the model is done efficiently using Diagonal Detector Overlapping Tomography – a generalization of the recently introduced Quantum Overlapping Tomography to the problem of reconstruction of readout noise with restricted locality. The procedure allows to characterize k-local measurement cross-talk on N-qubit device using O(k2klog(N)) circuits containing random combinations of X and identity gates. We perform experiments on 15 (23) qubits using IBM's (Rigetti's) devices to test both the noise model and the error-mitigation scheme, and obtain an average reduction of errors by a factor >22 (>5.5) compared to no mitigation. Interestingly, we find that correlations in the measurement noise do not correspond to the physical layout of the device. Furthermore, we study numerically the effects of readout noise on the performance of the Quantum Approximate Optimization Algorithm (QAOA). We observe in simulations that for numerous objective Hamiltonians, including random MAX-2-SAT instances and the Sherrington-Kirkpatrick model, the noise-mitigation improves the quality of the optimization. Finally, we provide arguments why in the course of QAOA optimization the estimates of the local energy (or cost) terms often behave like uncorrelated variables, which greatly reduces sampling complexity of the energy estimation compared to the pessimistic error analysis. We also show that similar effects are expected for Haar-random quantum states and states generated by shallow-depth random circuits.

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Section: Future Researchmentioning

confidence: 99%

Modeling and mitigation of cross-talk effects in readout noise with applications to the Quantum Approximate Optimization Algorithm

Maciejewski

Baccari

Zimborás

et al. 2021

Quantum

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“…To apply this protocol to large-scale simulations, we can break the full system into subsystems 33,41 to reduce the exponential scaling to polynomial scaling. Specifically, if the Hamiltonian is klocal, we can decompose the system into subsystems of size s ≥ 2k (see Fig.…”

Section: Continue Until the Largest Basis State Population Reachesmentioning

confidence: 99%

Practical verification protocols for analog quantum simulators

et al. 2021

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Analog quantum simulation is expected to be a significant application of near-term quantum devices. Verification of these devices without comparison to known simulation results will be an important task as the system size grows beyond the regime that can be simulated classically. We introduce a set of experimentally-motivated verification protocols for analog quantum simulators, discussing their sensitivity to a variety of error sources and their scalability to larger system sizes. We demonstrate these protocols experimentally using a two-qubit trapped-ion analog quantum simulator and numerically using models of up to five qubits.

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“…where q(r, s ) describes the permutation action of the Clifford gateÛ and φ q(r,s ) describes the associated phase factor. To determine the Choi dual state for the effective process on Bob's qudit alone, we take the partial trace with respect to all N E of Eve's ancilla qubits on both D-dimensional subsystems of the Choi dual state [38]…”

Section: A Clifford-group Restrictionmentioning

confidence: 99%

Clifford-group-restricted eavesdroppers in quantum key distribution

et al. 2020

Self Cite

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Quantum key distribution (QKD) promises provably secure cryptography, even to attacks from an all-powerful adversary. However, with quantum computing development lagging behind QKD, the assumption that there exists an adversary equipped with a universal fault-tolerant quantum computer is unrealistic for at least the nearfuture. Here, we explore the effect of restricting the eavesdropper's computational capabilities on the security of QKD and find that improved secret key rates are possible. Specifically, we show that for a large class of discrete variable protocols higher key rates are possible if the eavesdropper is restricted to a unitary operation from the Clifford group. Further, we consider Clifford-random channels consisting of mixtures of Clifford gates. We numerically calculate a secret-key-rate lower bound for BB84 with this restriction and show that, in contrast to the case of a single restricted unitary attack, the mixture of Clifford-based unitary attacks does not result in an improved key rate.

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Bootstrapping quantum process tomography via a perturbative ansatz

Cited by 45 publications

References 64 publications

Modeling and mitigation of cross-talk effects in readout noise with applications to the Quantum Approximate Optimization Algorithm

Modeling and mitigation of cross-talk effects in readout noise with applications to the Quantum Approximate Optimization Algorithm

Practical verification protocols for analog quantum simulators

Clifford-group-restricted eavesdroppers in quantum key distribution

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