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Quantum mechanics promises computational powers beyond the reach of classical computers. Current technology is on the brink of an experimental demonstration of the superior power of quantum computation compared to classical devices. For…

Quantum Physics · Physics 2019-04-02 Jelmer Renema , Valery Shchesnovich , Raul Garcia-Patron

We provide a polynomial-time classical algorithm for noisy quantum circuits. The algorithm computes the expectation value of any observable for any circuit, with a small average error over input states drawn from an ensemble (e.g. the…

Quantum Physics · Physics 2024-10-15 Thomas Schuster , Chao Yin , Xun Gao , Norman Y. Yao

We introduce a technique to estimate error-mitigated expectation values on noisy quantum computers. Our technique performs shadow tomography on a logical state to produce a memory-efficient classical reconstruction of the noisy density…

Quantum Physics · Physics 2022-03-15 Hong-Ye Hu , Ryan LaRose , Yi-Zhuang You , Eleanor Rieffel , Zhihui Wang

Magic states are essential for universal quantum computation and are widely viewed as a key source of quantum advantage, yet in realistic devices they are inevitably noisy. In this work, we characterize how noise on injected magic resources…

Quantum Physics · Physics 2026-01-21 Jiwon Heo , Sojeong Park , Changhun Oh

Quantum machine learning is often highlighted as one of the most promising practical applications for which quantum computers could provide a computational advantage. However, a major obstacle to the widespread use of quantum machine…

Quantum Physics · Physics 2024-07-09 Sofiene Jerbi , Casper Gyurik , Simon C. Marshall , Riccardo Molteni , Vedran Dunjko

We propose an efficient scheme for verifying quantum computations in the `high complexity' regime i.e. beyond the remit of classical computers. Previously proposed schemes remarkably provide confidence against arbitrarily malicious…

Quantum Physics · Physics 2017-05-24 Richard Jozsa , Sergii Strelchuk

Estimation of expectation values of incompatible observables is an essential practical task in quantum computing, especially for approximating energies of chemical and other many-body quantum systems. In this work we introduce a method for…

Quantum Physics · Physics 2023-03-14 Daniel McNulty , Filip B. Maciejewski , Michał Oszmaniec

One of the core research questions in the theory of quantum computing is to find out to what precise extent the classical simulation of a noisy quantum circuits is possible and where potential quantum advantages can set in. In this work, we…

Quantum Physics · Physics 2026-01-09 Janek Denzler , Jose Carrasco , Jens Eisert , Tommaso Guaita

The classical shadows protocol, introduced by Huang et al. [Nat. Phys. 16, 1050 (2020)], makes use of the median-of-means (MoM) estimator to efficiently estimate the expectation values of $M$ observables with failure probability $\delta$…

Quantum Physics · Physics 2025-06-25 Winston Fu , Dax Enshan Koh , Siong Thye Goh , Jian Feng Kong

Sampling noisy intermediate-scale quantum devices is a fundamental step that converts coherent quantum-circuit outputs to measurement data for running variational quantum algorithms that utilize gradient and Hessian methods in cost-function…

Quantum Physics · Physics 2023-07-04 Y. S. Teo

Classical shadows constitute a protocol to estimate the expectation values of a collection of M observables acting on O(1) qubits of an unknown n-qubit state with a number of measurements that is independent of n and that grows only…

Quantum Physics · Physics 2024-10-03 Giacomo De Palma , Tristan Klein , Davide Pastorello

Randomized protocols are procedures that incorporate probabilistic choices during their execution and they play a central role in quantum algorithms, spanning Hamiltonian simulation, noise mitigation, and measurement tasks. In practical…

Quantum Physics · Physics 2026-03-17 Davide Cugini , Touheed Anwar Atif , Yigit Subasi

We study the effect of shared non-signaling correlations for the problem of simulating a channel using noiseless communication in the one-shot setting. For classical channels, we show how to round any non-signaling-assisted simulation…

Quantum Physics · Physics 2024-11-18 Aadil Oufkir , Omar Fawzi , Mario Berta

Learning quantum state properties is both a fundamental and practical problem in quantum information theory. Classical shadows have emerged as an efficient method for estimating properties of unknown quantum states, with rigorous…

Quantum Physics · Physics 2026-03-30 Hugo Thomas , Ulysse Chabaud , Pierre-Emmanuel Emeriau

Quantum circuit simulators running on classical computers offer a vital platform for designing, testing, and optimizing quantum algorithms, driving innovation despite limited access to real quantum hardware. However, their scalability is…

Quantum Physics · Physics 2025-10-29 Gleb Kalachev , Pavel Mosharev , Zuoheng Zou , Pavel Panteleev , Man-Hong Yung

A wide variety of optimization techniques, both exact and heuristic, tend to be biased samplers. This means that when attempting to find multiple uncorrelated solutions of a degenerate Boolean optimization problem a subset of the solution…

Disordered Systems and Neural Networks · Physics 2019-05-14 Andrew J. Ochoa , Darryl C. Jacob , Salvatore Mandrà , Helmut G. Katzgraber

We generalize the classical shadow tomography scheme to a broad class of finite-depth or finite-time local unitary ensembles, known as locally scrambled quantum dynamics, where the unitary ensemble is invariant under local basis…

Quantum Physics · Physics 2025-10-27 Hong-Ye Hu , Soonwon Choi , Yi-Zhuang You

In this paper, we propose a novel quantum classifier utilizing dissipative engineering. Unlike standard quantum circuit models, the classifier consists of a central spin-qubit model. By subjecting the auxiliary qubits to carefully tailored…

Quantum Physics · Physics 2024-09-06 He Wang , Chuanbo Liu , Jin Wang

Classical shadows are a versatile tool to probe many-body quantum systems, consisting of a combination of randomised measurements and classical post-processing computations. In a recently introduced version of the protocol, the…

Quantum Physics · Physics 2025-04-14 Riccardo Cioli , Elisa Ercolessi , Matteo Ippoliti , Xhek Turkeshi , Lorenzo Piroli

Quantum machine learning uses principles from quantum mechanics to process data, offering potential advances in speed and performance. However, previous work has shown that these models are susceptible to attacks that manipulate input data…

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