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Measuring the state of quantum computers is a highly non-trivial task, with implications for virtually all quantum algorithms. We propose a novel scheme where identical copies of a quantum state are measured jointly so that all Pauli…

Quantum Physics · Physics 2025-09-03 Rick P. A. Simon , Zheng Shi , Charlie Nation , Andrew Jena , Luca Dellantonio

We study the dynamics of classical and quantum systems undergoing a continuous measurement of position by schematizing the measurement apparatus with an infinite set of harmonic oscillators at finite temperature linearly coupled to the…

Quantum Physics · Physics 2008-11-26 Carlo Presilla , Roberto Onofrio , Marco Patriarca

When a quantum system is monitored in continuous time, the result of the measurement is a stochastic process. When the output process is stationary, at least in the long run, the spectrum of the process can be introduced and its properties…

Quantum Physics · Physics 2009-10-09 Alberto Barchielli , Matteo Gregoratti

Quantum sensors outperform their classical counterparts in their estimation precision, given the same amount of resources. So far, quantum-enhanced sensitivity has been achieved by exploiting the superposition principle. This enhancement…

Quantum Physics · Physics 2022-10-05 Victor Montenegro , Gareth Siôn Jones , Sougato Bose , Abolfazl Bayat

Complete characterization of states and processes that occur within quantum devices is crucial for understanding and testing their potential to outperform classical technologies for communications and computing. However, solving this task…

Quantum Physics · Physics 2020-05-07 E. S. Tiunov , V. V. Tiunova , A. E. Ulanov , A. I. Lvovsky , A. K. Fedorov

We consider a dynamic protocol for quantum many-body systems, which enables to study the interplay between unitary Hamiltonian driving and random local projective measurements. While the unitary dynamics tends to increase entanglement,…

Statistical Mechanics · Physics 2020-07-15 Davide Rossini , Ettore Vicari

The restricted-path-integral (RPI) theory of continuous quantum measurements including the evolution of the measured systems and phenomenon of decoherence is reviewed. The measured system is considered as an open quantum system but without…

Quantum Physics · Physics 2007-05-23 Michael B. Mensky

Producing quantum states at random has become increasingly important in modern quantum science, with applications both theoretical and practical. In particular, ensembles of such randomly-distributed, but pure, quantum states underly our…

We present an iterative method to solve the multipartite quantum state estimation problem. We demonstrate convergence for any informationally complete set of generalized quantum measurements in every finite dimension. Our method exhibits…

Quantum Physics · Physics 2022-03-21 Daniel Uzcategui Contreras , Gabriel Senno , Dardo Goyeneche

In quantum information processing quantum operations are often processed alongside measurements which result in classical data. Due to the information gain of classical measurement outputs non-unitary dynamical processes can take place on…

Any optical quantum information processing machine would be comprised of fully-characterized constituent devices for both single state manipulations and tasks involving the interaction between multiple quantum optical states. Ideally for…

Quantum Physics · Physics 2015-05-18 Connor Kupchak , Samuel Rind , Bertus Jordaan , Eden Figueroa

Accurate and robust estimation of quantum process properties is crucial for quantum information processing and quantum many-body physics. Combining classical shadow tomography and randomized benchmarking, Helsen et al. introduced a method…

Quantum Physics · Physics 2024-12-02 Yuqing Wang , Guoding Liu , Zhenhuan Liu , Yifan Tang , Xiongfeng Ma , Hao Dai

State discrimination is a useful test problem with which to clarify the power and limitations of different classes of measurement. We consider the problem of discriminating between given states of a bi-partite quantum system via sequential…

Quantum Physics · Physics 2017-09-25 Sarah Croke , Stephen M. Barnett , Graeme Weir

Learning quantum Hamiltonians with high precision is important for quantum physics and quantum information science. We propose a multi-stage neural network framework that significantly enhances Hamiltonian learning precision through…

Quantum Physics · Physics 2025-03-11 Zhengjie Kang , Hao Li , Shuo Wang , Jiaojiao Li , Yuanjie Zhang , Zhihuang Luo

We present an efficient and robust protocol for quantum-enhanced sensing using a single qubit in the topological waveguide system. Our method relies on the topological-paired bound states, which are localized near the qubit and can be…

Quantum Physics · Physics 2025-08-08 Tao Zhang , Peng Xu , Jiazhong Hu , Xingze Qiu

Characterizing quantum systems is a fundamental task that enables the development of quantum technologies. Various approaches, ranging from full tomography to instances of classical shadows, have been proposed to this end. However, quantum…

Quantum Physics · Physics 2025-06-16 Franz J. Schreiber , Jens Eisert , Johannes Jakob Meyer

We formulate a quantum mechanical system consisting of a single discrete state coupled to an infinite ladder of equally-spaced states, the coupling between the two being given by a Lorentzian profile. Various limits of this system…

Quantum Physics · Physics 2026-01-13 Enes Kutay İşgörür , Osman Cevheroğlu , Arkadaş Özakın

We introduce a general scheme for sequential one-way quantum computation where static systems with long-living quantum coherence (memories) interact with moving systems that may possess very short coherence times. Both the generation of the…

Quantum Physics · Physics 2015-05-27 Augusto J. Roncaglia , Leandro Aolita , Alessandro Ferraro , Antonio Acin

The paradigm of measurement-based quantum computing (MBQC) starts from a highly entangled resource state on which unitary operations are executed through adaptive measurements and corrections ensuring determinism. This is set in contrast to…

Quantum Physics · Physics 2023-11-29 Thierry Nicolas Kaldenbach , Matthias Heller

The resources needed to conventionally characterize a quantum system are overwhelmingly large for high- dimensional systems. This obstacle may be overcome by abandoning traditional cornerstones of quantum measurement, such as general…

Quantum Physics · Physics 2016-05-17 Gregory A. Howland , Samuel H. Knarr , James Schneeloch , Daniel J. Lum , John C. Howell