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We study the efficiency of quantum tomographic reconstruction where the system under investigation (quantum target) is indirectly monitored by looking at the state of a quantum probe that has been scattered off the target. In particular we…

Quantum Physics · Physics 2012-03-02 A. De Pasquale , P. Facchi , V. Giovannetti , K. Yuasa

Quantum algorithms require accurate representations of electronic states on a quantum device, yet the approximation of electronic wave functions for strongly correlated systems remains a profound theoretical challenge, with existing methods…

Quantum Physics · Physics 2025-04-29 Dipanjali Halder , Dibyendu Mondal , Rahul Maitra

Quantum computing with qudits is an emerging approach that exploits a larger, more-connected computational space, providing advantages for many applications, including quantum simulation and quantum error correction. Nonetheless, qudits are…

Quantum computing devices are inevitably subject to errors. To leverage quantum technologies for computational benefits in practical applications, quantum algorithms and protocols must be implemented reliably under noise and imperfections.…

Quantum Physics · Physics 2022-07-18 Jihye Kim , Byungdu Oh , Yonuk Chong , Euyheon Hwang , Daniel K. Park

Quantum computers face inherent scaling challenges, a fact that necessitates investigation of distributed quantum computing systems, whereby scaling is achieved through interconnection of smaller quantum processing units. However,…

Quantum Physics · Physics 2026-01-21 Felix Burt , Kuan-Cheng Chen , Kin K. Leung

As Noisy Intermediate-Scale Quantum (NISQ) devices grow in number of qubits, determining good or even adequate parameter configurations for a given application, or for device calibration, becomes a cumbersome task. An evolutionary algorithm…

Quantum Physics · Physics 2021-07-15 Luke Mortimer , Marta P. Estarellas , Timothy P. Spiller , Irene D'Amico

It has recently been shown that there are efficient algorithms for quantum computers to solve certain problems, such as prime factorization, which are intractable to date on classical computers. The chances for practical implementation,…

Quantum Physics · Physics 2009-10-30 Adriano Barenco , Todd A. Brun , Ruediger Schack , Tim Spiller

Error mitigation (EM) methods are crucial for obtaining reliable results in the realm of noisy intermediate-scale quantum (NISQ) computers, where noise significantly impacts output accuracy. Some EM protocols are particularly efficient for…

Quantum Physics · Physics 2026-03-03 Thibault Scoquart , Hugo Perrin , Kyrylo Snizhko

Several combinatorial optimization problems can be solved with NISQ devices once that a corresponding quadratic unconstrained binary optimization (QUBO) form is derived. The aim of this work is to drastically reduce the variables needed for…

Quantum Physics · Physics 2026-02-25 Dario De Santis , Salvatore Tirone , Stefano Marmi , Vittorio Giovannetti

In the emergent realm of quantum computing, the Variational Quantum Eigensolver (VQE) stands out as a promising algorithm for solving complex quantum problems, especially in the noisy intermediate-scale quantum (NISQ) era. However, the…

Quantum Physics · Physics 2024-03-13 Subhasree Bhattacharjee , Soumyadip Sarkar , Kunal Das , Bikramjit Sarkar

The successful implementation of algorithms on quantum processors relies on the accurate control of quantum bits (qubits) to perform logic gate operations. In this era of noisy intermediate-scale quantum (NISQ) computing, systematic…

We propose a noise-mitigation quantum simulation strategy for near-term quantum devices based on Quantum Circuit Learning (QCL), which is in particular effective for integrable quantum spin chains. The method trains a shallow variational…

Quantum Physics · Physics 2026-05-01 Wenlong Zhao , Yimeng Zhang , Yan Guo , Yufan Cui , Zhuohang Wang , Rui-Dong Zhu

We outline a proposal to test quantum mechanics in the high-complexity regime using noisy intermediate-scale quantum (NISQ) devices. The procedure involves simulating a non-Clifford random circuit, followed by its inverse, and then checking…

Quantum Physics · Physics 2022-08-26 Kevin Slagle

Noise is the central obstacle to building large-scale quantum computers. Quantum systems with sufficiently uncorrelated and weak noise could be used to solve computational problems that are intractable with current digital computers. There…

Quantum Physics · Physics 2021-04-19 Robin Harper , Steven T. Flammia , Joel J. Wallman

Gate-based universal quantum computation is formulated in terms of two types of operations: local single-qubit gates, which are typically easily implementable, and two-qubit entangling gates, whose faithful implementation remains one of the…

Quantum Physics · Physics 2023-10-18 Xiaoqin Gao , Paul Appel , Nicolai Friis , Martin Ringbauer , Marcus Huber

Quantum Recurrent Neural Networks (QRNNs) are robust candidates for modelling and predicting future values in multivariate time series. However, the effective implementation of some QRNN models is limited by the need for mid-circuit…

Quantum Physics · Physics 2025-01-31 José Daniel Viqueira , Daniel Faílde , Mariamo M. Juane , Andrés Gómez , David Mera

We consider a generalisation of Ekert's entanglement-based quantum cryptographic protocol where qubits are replaced by qu$N$its (i.e., N-dimensional systems). In order to study its robustness against optimal incoherent attacks, we derive…

Quantum Physics · Physics 2009-11-10 Thomas Durt , Dagomir Kaszlikowski , Jing-Ling Chen , L. C. Kwek

The entanglement entropy of a subsystem $A$ of a quantum system is expressed, in the replica method, through analytic continuation with respect to n of the trace of the n-th power of the reduced density matrix $\tr\rho_A^n$. We study the…

Statistical Mechanics · Physics 2010-03-25 F. Gliozzi , L. Tagliacozzo

Some of the computational limitations in solving the nuclear many-body problem could be overcome by utilizing quantum computers. The nuclear shell-model calculations providing deeper insights into the properties of atomic nuclei, is one…

Quantum Physics · Physics 2026-05-25 Nifeeya Singh , Pooja Siwach , P. Arumugam

A universal fault-tolerant quantum computer holds the promise to speed up computational problems that are otherwise intractable on classical computers; however, for the next decade or so, our access is restricted to noisy intermediate-scale…

Quantum Physics · Physics 2023-02-22 Archismita Dalal , Amara Katabarwa