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Motivated by the limited qubit capacity of current quantum systems, we study the quantum sample complexity of $k$-qubit quantum operators, i.e., operations applicable on only $k$ out of $d$ qubits. The problem is studied according to the…

Quantum Physics · Physics 2023-04-26 Mohsen Heidari , Wojciech Szpankowski

While deep ensembles are widely considered to be the default method for uncertainty quantification in deep learning, their effectiveness for graph-structured data is often simply assumed based on successes in domains like computer vision.…

Machine Learning · Computer Science 2026-05-22 Pedro C. Vieira , Pedro Ribeiro , Viacheslav Borovitskiy

Learning properties of quantum states from measurement data is a fundamental challenge in quantum information. The sample complexity of such tasks depends crucially on the measurement primitive. While shadow tomography achieves…

Quantum Physics · Physics 2025-10-10 Jan Nöller , Viet T. Tran , Mariami Gachechiladze , Richard Kueng

Scrambling of quantum information is an important feature at the root of randomization and benchmarking protocols, the onset of quantum chaos, and black-hole physics. Unscrambling this information is possible given perfect knowledge of the…

Quantum Physics · Physics 2024-03-06 Lorenzo Leone , Salvatore F. E. Oliviero , Seth Lloyd , Alioscia Hamma

What makes a class of quantum circuits efficiently classically simulable on average? I present a framework that applies harmonic analysis of groups to circuits with a structure encoded by group parameters. Expanding the circuits in a…

Quantum Physics · Physics 2024-10-18 Cristina Cirstoiu

We present a quantum process-tomography protocol based on a low-degree ansatz for the quantum channel, i.e. when it can be expressed as a fixed-degree polynomial in terms of Pauli operators. We demonstrate how to perform tomography of such…

Quantum Physics · Physics 2026-01-09 Marianna Crupi , J. Ignacio Cirac , Flavio Baccari

A general framework describing the statistical discrimination of an ensemble of quantum channels is given by the name of quantum reading. Several tools can be applied in quantum reading to reduce the error probability in distinguishing the…

Quantum Physics · Physics 2022-06-09 Francisco Revson Fernandes Pereira , Stefano Mancini

We establish a classical heuristic algorithm for exactly computing quantum probability amplitudes. Our algorithm is based on mapping output probability amplitudes of quantum circuits to evaluations of the Tutte polynomial of graphic…

Quantum Physics · Physics 2021-09-28 Ryan L. Mann

Given a quantum Markovian noise model, we study the maximum dimension of a classical or quantum system that can be stored for arbitrarily large time. We show that, unlike the fixed time setting, in the limit of infinite time, the classical…

Quantum Physics · Physics 2025-02-27 Omar Fawzi , Mizanur Rahaman , Mostafa Taheri

Simulating dynamics of physical systems is a key application of quantum computing, with potential impact in fields such as condensed matter physics and quantum chemistry. However, current quantum algorithms for Hamiltonian simulation yield…

Randomized algorithms are crucial subroutines in quantum computing, but the requirement to execute many types of circuits on a real quantum device has been challenging to their extensive implementation. In this study, we propose an…

Quantum Physics · Physics 2026-04-23 Shu Kanno , Ikko Hamamura , Rudy Raymond , Qi Gao , Naoki Yamamoto

We introduce a direct estimation framework for reconstructing multiple density matrix elements of an unknown quantum state using classical shadow tomography. Traditional direct measurement protocols (DMPs), while effective for individual…

Quantum Physics · Physics 2025-05-22 Yu Wang

Quantum algorithms exploiting real-time evolution under a target Hamiltonian have demonstrated remarkable efficiency in extracting key spectral information. However, the broader potential of these methods, particularly beyond ground state…

Deep learning has seen substantial achievements, with numerical and theoretical evidence suggesting that singularities of statistical models are considered a contributing factor to its performance. From this remarkable success of classical…

Quantum Physics · Physics 2024-11-26 Hiroshi Yano , Yota Maeda , Naoki Yamamoto

Long periodic orbits constitute a serious drawback in Gutzwiller's theory of chaotic systems, and then it would be desirable that other classical invariants, not suffering from the same problem, could be used in the quantization of such…

Chaotic Dynamics · Physics 2009-11-10 D. A. Wisniacki , E. Vergini , R. M. Benito , F. Borondo

In this paper, we investigate the classicality and quantumness of a quantum ensemble. We define a quantity called classicality to characterize how classical a quantum ensemble is. An ensemble of commuting states that can be manipulated…

Quantum Physics · Physics 2015-05-20 Xuanmin Zhu , Shengshi Pang , Shengjun Wu , Quanhui Liu

Giving a convincing experimental evidence of the quantum supremacy over classical simulations is a challenging goal. Noise is considered to be the main problem in such a demonstration, hence it is urgent to understand the effect of noise.…

Quantum Physics · Physics 2022-03-08 Valery Shchesnovich

We present a classical model for bulk-ensemble NMR quantum computation: the quantum state of the NMR sample is described by a probability distribution over the orientations of classical tops, and quantum gates are described by classical…

Quantum Physics · Physics 2008-12-18 R. Schack , C. M. Caves

We investigate the amount of noise required to turn a universal quantum gate set into one that can be efficiently modelled classically. This question is useful for providing upper bounds on fault tolerant thresholds, and for understanding…

Quantum Physics · Physics 2007-05-23 S. Virmani , Susana F. Huelga , Martin B. Plenio

Cross-platform verification is the task of comparing the output states produced by different physical platforms using solely local quantum operations and classical communication. While protocols have previously been suggested for this task,…

Quantum Physics · Physics 2025-09-22 Marcel Hinsche , Marios Ioannou , Sofiene Jerbi , Lorenzo Leone , Jens Eisert , Jose Carrasco
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