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The Hadamard test is naturally suited for the intermediate regime between the current era of noisy quantum devices and complete fault tolerance. Its applications use measurements of the auxiliary qubit to extract information, but disregard…

Quantum Physics · Physics 2025-10-21 Paul K. Faehrmann , Jens Eisert , Richard Kueng

Understanding the capabilities of classical simulation methods is key to identifying where quantum computers are advantageous. Not only does this ensure that quantum computers are used only where necessary, but also one can potentially…

This study systematically benchmarks classical optimization strategies for the Quantum Approximate Optimization Algorithm when applied to Generalized Mean-Variance Problems under near-term Noisy Intermediate-Scale Quantum conditions. We…

Quantum Physics · Physics 2025-11-13 Tomáš Bezděk , Haomu Yuan , Vojtěch Novák , Silvie Illésová , Martin Beseda

We identify a broad class of physical processes in an optical quantum circuit that can be efficiently simulated on a classical computer: this class includes unitary transformations, amplification, noise, and measurements. This…

Quantum Physics · Physics 2007-05-23 Stephen D. Bartlett , Barry C. Sanders

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

Boson sampling is one of the leading protocols for demonstrating a quantum advantage, but the theory of how this protocol responds to noise is still incomplete. We extend the theory of classical simulation of boson sampling with partial…

Quantum Physics · Physics 2025-03-07 S. N. van den Hoven , E. Kanis , J. J. Renema

Quantum many-body systems provide a unique platform for exploring the rich interplay between chaos, randomness, and complexity. In a recently proposed paradigm known as deep thermalization, random quantum states of system A are generated by…

Quantum Physics · Physics 2025-06-17 Wai-Keong Mok , Tobias Haug , Adam L. Shaw , Manuel Endres , John Preskill

Constrained optimization of the parameters of a simulator plays a crucial role in a design process. These problems become challenging when the simulator is stochastic, computationally expensive, and the parameter space is high-dimensional.…

Optimization and Control · Mathematics 2023-11-28 Atul Agrawal , Kislaya Ravi , Phaedon-Stelios Koutsourelakis , Hans-Joachim Bungartz

Detecting nonclassical properties that do not allow classical interpretation of photoelectric counting events is one of the crucial themes in quantum optics. Observation of individual nonclassical effects for a single-mode field, however,…

Quantum Physics · Physics 2015-05-13 Juhui Lee , Jaewan Kim , Hyunchul Nha

Classical simulation is important because it sets a benchmark for quantum computer performance. Classical simulation is currently the only way to exercise larger numbers of qubits. To achieve larger simulations, sparse matrix processing is…

Quantum Physics · Physics 2007-05-23 John Robert Burger

In recent times, Variational Quantum Circuits (VQC) have been widely adopted to different tasks in machine learning such as Combinatorial Optimization and Supervised Learning. With the growing interest, it is pertinent to study the…

Quantum Physics · Physics 2022-12-13 Dheeraj Peddireddy , Vipul Bansal , Vaneet Aggarwal

We present a robust shadow estimation protocol for wide classes of low-depth measurement circuits that mitigates noise as long as the effective measurement map including noise is locally unitarily invariant. This is in practice an excellent…

Quantum Physics · Physics 2025-03-26 Renato M. S. Farias , Raghavendra D. Peddinti , Ingo Roth , Leandro Aolita

Classification of quantum data is essential for quantum machine learning and near-term quantum technologies. In this paper, we propose a new hybrid quantum-classical framework for supervised quantum learning, which we call Variational…

Quantum Physics · Physics 2020-12-16 Guangxi Li , Zhixin Song , Xin Wang

In the noisy intermediate scale quantum (NISQ) era, the control over the qubits is limited due to the errors caused by quantum decoherence, crosstalk, and imperfect calibration. Hence, it is necessary to reduce the size of the large-scale…

Quantum Physics · Physics 2024-09-24 Jishnu Mahmud , Shaikh Anowarul Fattah

Classical ghost imaging is a new paradigm in imaging where the image of an object is not measured directly with a pixelated detector. Rather, the object is subject to a set of illumination patterns and the total interaction of the object,…

Image and Video Processing · Electrical Eng. & Systems 2023-08-02 Andrew M. Kingston , Lindon Roberts , Alaleh Aminzadeh , Daniele Pelliccia , Imants D. Svalbe , David M. Paganin

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…

Estimating many local expectation values over time is a central measurement bottleneck in quantum simulation and device characterization. We study the task of reconstructing the Pauli-signal matrix $S_{ij}=\text{Tr}(O_i \rho(t_j))$ for a…

Quantum Physics · Physics 2026-02-16 Joseph Barreto , Daniel Lidar

The development of new techniques to improve measurements is crucial for all sciences. By employing quantum systems as sensors to probe some physical property of interest allows the application of quantum resources, such as coherent…

Quantum Physics · Physics 2019-05-15 G. H. Aguilar , M. A. de Souza , R. M. Gomes , J. Thompson , M. Gu , L. C. Céleri , S. P. Walborn

An optimal estimator of quantum states based on a modified Kalman Filter is presented in this work. Such estimator acts after state measurement, allowing to obtain an optimal estimation of quantum state resulting in the output of any…

Quantum Physics · Physics 2014-06-20 Mario Mastriani

Recovering shadows is an important step for many vision algorithms. Current approaches that work with time-lapse sequences are limited to simple thresholding heuristics. We show these approaches only work with very careful tuning of…

Computer Vision and Pattern Recognition · Computer Science 2013-04-16 Austin Abrams , Chris Hawley , Kylia Miskell , Adina Stoica , Nathan Jacobs , Robert Pless
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