Quantum 5, 498 (2021). https://doi.org/10.22331/q-2021-07-08-498 The Wigner’s friend paradox concerns one of the most puzzling problems of quantum mechanics: the consistent description of multiple nested observers. Recently, a variation of Wigner’s gedankenexperiment, introduced by Frauchiger […]
Quantum 5, 497 (2021). https://doi.org/10.22331/q-2021-07-06-497 This paper presents “Stim”, a fast simulator for quantum stabilizer circuits. The paper explains how Stim works and compares it to existing tools. With no foreknowledge, Stim can analyze a […]
Quantum 5, 496 (2021). https://doi.org/10.22331/q-2021-07-05-496 We study supervised learning algorithms in which a quantum device is used to perform a computational subroutine – either for prediction via probability estimation, or to compute a kernel via […]
Quantum 5, 495 (2021). https://doi.org/10.22331/q-2021-07-05-495 We consider simulating quantum systems on digital quantum computers. We show that the performance of quantum simulation can be improved by simultaneously exploiting commutativity of the target Hamiltonian, sparsity of […]
Quantum 5, 494 (2021). https://doi.org/10.22331/q-2021-07-05-494 One of the lowest-order corrections to Gaussian quantum mechanics in infinite-dimensional Hilbert spaces are Airy functions: a uniformization of the stationary phase method applied in the path integral perspective. We […]
Quantum 5, 493 (2021). https://doi.org/10.22331/q-2021-07-01-493 Certification of nonlocality of quantum mechanics is an important fundamental test that typically requires prolonged data collection and is only revealed in an in-depth analysis. These features are often particularly […]
Quantum 5, 492 (2021). https://doi.org/10.22331/q-2021-07-01-492 We present a hardware agnostic error mitigation algorithm for near term quantum processors inspired by the classical Lanczos method. This technique can reduce the impact of different sources of noise […]
Quantum 5, 491 (2021). https://doi.org/10.22331/q-2021-07-01-491 The quantum approximate optimization algorithm (QAOA) is a prospective near-term quantum algorithm due to its modest circuit depth and promising benchmarks. However, an external parameter optimization required in QAOA could […]
Quantum 5, 490 (2021). https://doi.org/10.22331/q-2021-07-01-490 We propose a parameter estimation protocol for generalized Pauli channels acting on $d$-dimensional Hilbert space. The salient features of the proposed method include product probe states and measurements, the number […]
Quantum 5, 489 (2021). https://doi.org/10.22331/q-2021-07-01-489 We show that the quantum Fisher information attained in an adiabatic approach to critical quantum metrology cannot lead to the Heisenberg limit of precision and therefore $regular$ quantum metrology under […]
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