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The dynamics of many open quantum systems are described by stochastic master equations. In the discrete-time case, we recall the structure of the derived quantum filter governing the evolution of the density operator conditioned to the…

Optimization and Control · Mathematics 2015-03-23 Pierre Six , Philippe Campagne-Ibarcq , Landry Bretheau , Benjamin Huard , Pierre Rouchon

In this article, we present a novel approach to investigating entanglement in the context of quantum computing. Our methodology involves analyzing reduced density matrices at different stages of a quantum algorithm's execution and…

Quantum Physics · Physics 2024-03-14 Ruge Lin

Probabilities of the outcomes of consecutive quantum measurements can be obtained by construction probability amplitudes, thus implying unitary evolution of the measured system, broken each time a measurement is made. In practice, the…

Quantum Physics · Physics 2022-07-13 D. Sokolovski

We propose to use neural networks to estimate the rates of coherent and incoherent processes in quantum systems from continuous measurement records. In particular, we adapt an image recognition algorithm to recognize the patterns in…

Quantum Physics · Physics 2017-11-15 Eliska Greplova , Christian Kraglund Andersen , Klaus Mølmer

A pivotal task in quantum metrology, and quantum parameter estimation in general, is to de- sign schemes that achieve the highest precision with given resources. Standard models of quantum metrology usually assume the dynamics is fixed, the…

Quantum Physics · Physics 2017-07-18 Jing Liu , Haidong Yuan

The effect of quantum steering describes a possible action at a distance via local measurements. In the last few years, several criteria have been proposed to detect this type of correlation in quantum systems. However, there are few…

Quantum Physics · Physics 2024-04-16 L. Maquedano , A. C. S. Costa

Quantum metrology holds the promise of an early practical application of quantum technologies, in which measurements of physical quantities can be made with much greater precision than what is achievable with classical technologies. In this…

Quantum Physics · Physics 2021-01-27 Jasminder S. Sidhu , Pieter Kok

In quantum theory, the inescapable interaction between a system and its surroundings would lead to a loss of coherence and leakage of information into the environment. An effective approach to retain the quantum characteristics of the…

Quantum Physics · Physics 2025-08-29 Guohui Dong , Yao Yao

Quantum metrology is a general term for methods to precisely estimate the value of an unknown parameter by actively using quantum resources. In particular, some classes of entangled states can be used to significantly suppress the…

Quantum Physics · Physics 2015-05-01 Takanori Sugiyama

In this thesis we consider primarily the dynamics of quantum systems subjected to continuous observation. In the Schr\"{o}dinger picture the evolution of a continuously monitored quantum system, referred to as a `quantum trajectory', may be…

Quantum Physics · Physics 2009-09-25 K. Jacobs

A common knowledge suggests that trajectories of particles in quantum mechanics always have quantum uncertainties. These quantum uncertainties set by the Heisenberg uncertainty principle limit precision of measurements of fields and forces,…

Quantum Physics · Physics 2015-02-11 Eugene S. Polzik , Klemens Hammerer

A usual assumption in quantum estimation is that the unknown parameter labels the possible states of the system, while it influences neither the sample space of outcomes nor the measurement aimed at extracting information on the parameter…

Quantum Physics · Physics 2017-01-18 Luigi Seveso , Matteo A. C. Rossi , Matteo G. A. Paris

The measurement process in quantum mechanics is usually described by the von Neumann projection postulate, which forms a basic constituent of the laws of quantum mechanics. Since this postulate requires the outside observer of the system,…

Quantum Physics · Physics 2009-11-11 Masahiro Morikawa , Akika Nakamichi

In quantum metrology, one of the major applications of quantum technologies, the ultimate precision of estimating an unknown parameter is often stated in terms of the Cram\'er-Rao bound. Yet, the latter is no longer guaranteed to carry an…

The possibility of determining the state of a quantum system after a continuous measurement of position is discussed in the framework of quantum trajectory theory. Initial lack of knowledge of the system and external noises are accounted…

Quantum Physics · Physics 2009-10-31 A. C. Doherty , S. M. Tan , A. S. Parkins , D. F. Walls

We perform stochastic simulations of the quantum Zeno and anti-Zeno effects for two level system and for the decaying one. Instead of simple projection postulate approach, a more realistic model of a detector interacting with the…

Quantum Physics · Physics 2007-05-23 J. Ruseckas , B. Kaulakys

Quantum trajectory theory, developed largely in the quantum optics community to describe open quantum systems subjected to continuous monitoring, has applications in many areas of quantum physics. In this paper I present a simple model,…

Quantum Physics · Physics 2009-11-07 Todd A. Brun

We investigate the behavior of quantum trajectories conditioned on measurement outcomes. Under a condition related to the absence of so-called dark subspaces, K\"{u}mmerer and Maassen had shown that such trajectories almost surely purify in…

Quantum Physics · Physics 2026-01-21 Maël Bompais , Nina H. Amini , Juan P. Garrahan , Mădălin Guţă

Quantum metrology is an auspicious discipline of quantum information which is currently witnessing a surge of experimental breakthroughs and theoretical developments. The main goal of quantum metrology is to estimate unknown parameters as…

Quantum Physics · Physics 2022-01-06 Nathan Shettell

It is proposed a possible new approach of quantum measurements (QMS), disconnected of the traditional interpretation of uncertainty relations and independent of any appeal to the strange idea of collapse (reduction) of wave functions. The…

Quantum Physics · Physics 2007-05-23 S. Dumitru