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Quantum metrology utilizes entanglement for improving the sensitivity of measurements. Up to now the focus has been on the measurement of just one out of two non-commuting observables. Here we demonstrate a laser interferometer that…

Recent development in quantum information sciences and technologies, especially building programmable quantum computers, provide us new opportunities to study fundamental aspects of quantum mechanics. We propose qubit models to emulate the…

Quantum Physics · Physics 2022-06-29 Meng-Jun Hu , Yanbei Chen , Yiqiu Ma , Xiang Li , Yubao Liu , Yong-Sheng Zhang , Haixing Miao

We derive the class of covariant measurements which are optimal according to the maximum likelihood criterion. The optimization problem is fully resolved in the case of pure input states, under the physically meaningful hypotheses of…

In this article we propose an alternate model for the so called {\it protective measurements}, more appropriately {\it adiabatic measurements} of a spin 1/2 system where the {\it apparatus} is also a quantum system with a {\em finite…

Quantum Physics · Physics 2007-05-23 Anirban Das , N. D. Hari Dass

We construct a rigourous model of quantum measurement. A two-state model of a negative temperature amplifier, such as a laser, is taken to a classical thermodynamic limit. In the limit, it becomes a classical measurement apparatus obeying…

Quantum Physics · Physics 2007-05-23 Joseph F. Johnson

Single quantum system, such as Unruh-DeWitt detector, can be used to determine absolute acceleration by local measurements on a quantum field. To show this, we consider two kinematically indistinguishable scenarios: an inertial observer,…

Quantum Physics · Physics 2011-05-09 Andrzej Dragan , Ivette Fuentes , Jorma Louko

Improved measurement techniques are central to technological development and foundational scientific exploration. Quantum optics relies upon detectors sensitive to non-classical features of light, enabling precise tests of physical laws and…

Quantum Physics · Physics 2014-07-18 Merlin Cooper , Michal Karpinski , Brian J. Smith

Under the principle that quantum mechanical observables are invariant under relevant symmetry transformations, we explore how the usual, non-invariant quantities may capture measurement statistics. Using a relativisation mapping, viewed as…

Quantum Physics · Physics 2017-04-05 Leon Loveridge , Paul Busch , Takayuki Miyadera

Measurements of the position of a relativistic particle is considered in the framework of the Restricted-Path-Integral (RPI) approach. The amplitude describing such a measurement is shown to be exponentially small outside the light cone of…

Quantum Physics · Physics 2009-11-06 Michael B. Mensky , Horst von Borzeszkowski

Starting from a new principle inspired by quantum tomography rather than from Born's rule, this paper gives a self-contained deductive approach to quantum mechanics and quantum measurement. A suggestive notion for what constitutes a quantum…

Quantum Physics · Physics 2024-05-22 Arnold Neumaier

This is the first in a series of papers aiming to develop a relativistic quantum information theory in terms of unequal-time correlation functions in quantum field theory. In this work, we highlight two formalisms which together can provide…

Quantum Physics · Physics 2023-02-15 Charis Anastopoulos , Bei-Lok Hu , Konstantina Savvidou

We first review and critically examine some basic concepts and ambiguities related to quantum mechanics and quantum measurement to understand the success and shortcomings of current theories. We also touch on ideas regarding expression of…

Quantum Physics · Physics 2009-11-05 Fariel Shafee

A solution to the second measurement problem, determining what prior microscopic properties can be inferred from measurement outcomes ("pointer positions"), is worked out for projective and generalized (POVM) measurements, using consistent…

Quantum Physics · Physics 2017-09-20 Robert B. Griffiths

We prove that the Hilbert space description of all joint von Neumann measurements on a quantum state can be reproduced in terms of a single measure space ({\Omega}, F, {\mu}) with a normalized real-valued measure {\mu}, that is, in terms of…

Quantum Physics · Physics 2012-10-12 Elena R. Loubenets

Counting statistics of charge transfers in a point contact interacting with an arbitrary quantum system is studied. The theory for the charge specific density matrix is developed, allowing the evaluation of the probability of the outcome of…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 J. Rammer , A. L. Shelankov , J. Wabnig

Quantum metrology studies the ultimate limit of precision in estimating a physical quantity if quantum strategies are exploited. Here we investigate the evolution of a two-level atom as a detector which interacts with a massless scalar…

General Relativity and Quantum Cosmology · Physics 2015-01-28 Zehua Tian , Jieci Wang , Heng Fan , Jiliang Jing

Quantum states and measurements exhibit wave-like --- continuous, or particle-like --- discrete, character. Hybrid discrete-continuous photonic systems are key to investigating fundamental quantum phenomena, generating superpositions of…

Since quantum field theories do not possess proper position observables, Unruh-DeWitt detector models serve as a key theoretical tool for extracting localized spatio-temporal information from quantum fields. Most studies have been limited,…

Quantum Physics · Physics 2016-01-26 Daniel Hümmer , Eduardo Martin-Martinez , Achim Kempf

In order to address the measurement problem of quantum theory we make the assumption that quantum state reduction should be regarded as a genuine physical process deserving of a dynamical description. Generalizing the nonrelativistic…

Quantum Physics · Physics 2015-05-27 Daniel Bedingham

Consistency with relativistic causality narrows down dramatically the class of measurable observables. We argue that by weakening the preparation role of ideal measurements, many of these observables become measurable. Particularly, we show…

Quantum Physics · Physics 2009-11-07 Berry Groisman , Benni Reznik
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