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Monitored quantum circuits offer great perspectives for exploring the interplay of quantum information and complex quantum dynamics. These systems could realize the extensively studied entanglement and purification phase transitions, as…

Quantum Physics · Physics 2025-07-08 Moein N. Ivaki , Teemu Ojanen , Ali G. Moghaddam

Currently, there is no systematic way to describe a quantum process with memory solely in terms of experimentally accessible quantities. However, recent technological advances mean we have control over systems at scales where memory effects…

We study the problem of estimating frequency response functions of systems of coupled, classical harmonic oscillators using a quantum computer. The functional form of these response functions can be mapped to a corresponding eigenproblem of…

Quantum Physics · Physics 2025-11-14 Sven Danz , Mario Berta , Stefan Schröder , Pascal Kienast , Frank K. Wilhelm , Alessandro Ciani

We present a quantum algorithmic framework for simulating phase-contrast transmission electron microscopy (CTEM) image formation using a fault-tolerant, gate-based quantum circuit model. The electron wavefield on an $N\times N$ grid is…

Quantum Physics · Physics 2026-02-17 Sean D. Lam , Roberto dos Reis

We consider the continuous-time version of our recently proposed quantum theory of optical temporal phase and instantaneous frequency [Tsang, Shapiro, and Lloyd, Phys. Rev. A 78, 053820 (2008)]. Using a state-variable approach to…

Quantum Physics · Physics 2009-05-21 Mankei Tsang , Jeffrey H. Shapiro , Seth Lloyd

Nonlinear properties of quantum states are essential to quantum information and many-body physics, but assessing them experimentally is challenging, as it typically requires multi-copy operations or a large number of measurement settings.…

Quantum Physics · Physics 2026-05-12 Zihao Li , Datong Chen , Dayue Qin , Yuxiang Yang , You Zhou

Modelling the electrical response of multi-level quantum systems at finite frequency has been typically performed in the context of two incomplete paradigms: (i) input-output theory, which is valid at any frequency but neglects dynamic…

Mesoscale and Nanoscale Physics · Physics 2025-10-14 L. Peri , M. Benito , C. J. B. Ford , M. F. Gonzalez-Zalba

The well-known algorithm for quantum phase estimation requires that the considered unitary is available as a conditional transformation depending on the quantum state of an ancilla register. We present an algorithm converting an unknown…

Quantum Physics · Physics 2007-05-23 Dominik Janzing

We propose a quantum algorithm for finding eigenvalues of non-unitary matrices. We show how to construct, through interactions in a quantum system and projective measurements, a non-Hermitian or non-unitary matrix and obtain its eigenvalues…

Quantum Physics · Physics 2010-12-07 Hefeng Wang , Lian-Ao Wu , Yu-xi Liu , Franco Nori

Motivated by far-reaching applications ranging from quantum simulations of complex processes in physics and chemistry to quantum information processing, a broad effort is currently underway to build large-scale programmable quantum systems.…

The efficiency of parameter estimation of quantum channels is studied in this paper. We introduce the concept of programmable parameters to the theory of estimation. It is found that programmable parameters obey the standard quantum limit…

Quantum Physics · Physics 2010-03-17 Zhengfeng Ji , Guoming Wang , Runyao Duan , Yuan Feng , Mingsheng Ying

In this paper we study the quantum phase properties of {\it "nonlinear coherent states"} and {\it "solvable quantum systems with discrete spectra"} using the Pegg-Barnett formalism in a unified approach. The presented procedure will then be…

Quantum Physics · Physics 2010-11-11 G. R. Honarasa , M. K. Tavassoly , M. Hatami

Determination of the quantum nature of correlations between two spatially separated systems plays a crucial role in quantum information science. Of particular interest is the questions of if and how these correlations enable quantum…

Quantum Physics · Physics 2017-09-27 Farid Shahandeh , Austin P. Lund , Timothy C. Ralph

Bayesian quantum estimation provides a robust framework for quantum technologies, especially in scenarios with limited data and minimal prior information. Yet, its application to continuous-variable Gaussian systems has remained limited and…

Quantum Physics · Physics 2026-05-19 Edward Gandar , Jesús Rubio

In this thesis, we investigate whether quantum algorithms can be used in the field of machine learning for both long and near term quantum computers. We will first recall the fundamentals of machine learning and quantum computing and then…

Quantum Physics · Physics 2021-11-08 Jonas Landman

We propose an approach to measure the quantum phase of an electron in a non-Abelian system using the algorithm of Quantum Phase Estimation (QPE). The discrete-path systems were previously studied in the context of square or rectangular…

Quantum Physics · Physics 2025-09-15 Seng Ghee Tan , Son-Hsien Chen , Ying-Cheng Yang , Yen-Fu Chen , Yen-Lin Chen , Chia-Hsiu Hsieh

Quantum circuit complexity is a fundamental concept whose importance permeates quantum information, computation, many-body physics and high-energy physics. While extensively studied in closed systems, its characterization and behaviors in…

Quantum Physics · Physics 2025-08-28 Zhenyu Du , Zi-Wen Liu , Xiongfeng Ma

Many optimization methods for training variational quantum algorithms are based on estimating gradients of the cost function. Due to the statistical nature of quantum measurements, this estimation requires many circuit evaluations, which is…

Quantum Physics · Physics 2022-10-14 Lennart Bittel , Jens Watty , Martin Kliesch

In a standard Quantum Sensing (QS) task one aims at estimating an unknown parameter $\theta$, encoded into an $n$-qubit probe state, via measurements of the system. The success of this task hinges on the ability to correlate changes in the…

In this note we point out the fact that the proper conceptual setting of quantum computation is the theory of Linear Time Invariant systems. To convince readers of the utility of the approach, we introduce a new model of computation based…

Quantum Physics · Physics 2007-05-23 H. Gopalkrishna Gadiyar , K. M. Sangeeta Maini , R. Padma , H. S. Sharatchandra