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A measurement consists in coupling a system to a probe and reading the output of the probe to gather information about the system. The weaker the coupling, the smaller the back-action on the system, but also the less information conveyed.…

Quantum Physics · Physics 2012-11-13 Antonio Di Lorenzo , José Carlos Egues

Throughout quantum mechanics there is statistical balance, in the collective response of an ensemble of systems to differing measurement types. Statistical balance is a core feature of quantum mechanics, underlying quantum mechanical…

Quantum Physics · Physics 2022-10-31 Brian Drummond

By analyzing the concept of contextuality (Bell-Kochen-Specker) in terms of pre-and-post-selection (PPS), it is possible to assign definite values to observables in a new and surprising way. Physical reasons are presented for restrictions…

Quantum Physics · Physics 2009-11-13 Jeff Tollaksen

A number of issues related to measurement show that self-consistency is lacking in quantum mechanics as this theory has been generally understood. Each issue is presented as a point in this paper. Each point can be resolved by incorporating…

General Physics · Physics 2007-05-23 D. M. Snyder

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems…

In conventional measurement, to reach the greatest accuracy of parameter estimation, all samples must be measured since each independent sample contains the same quantum Fisher information. In postselected metrology, postselection can…

A new ontological view of the quantum measurement processes is given, which has bearings on many broader issues in the foundations of quantum mechanics as well. In this scenario a quantum measurement is a non-equilibrium phase transition in…

Quantum Physics · Physics 2007-05-23 Xiaolei Zhang

The properties which give quantum mechanics its unique character - unitarity, complementarity, non-commutativity, uncertainty, nonlocality - derive from the algebraic structure of Hermitian operators acting on the wavefunction in complex…

Quantum Physics · Physics 2022-09-14 Tim Palmer

This paper proposes an experiment designed to distinguish between competing interpretations of quantum mechanics: those that involve wave function collapse and those that assume purely unitary evolution. The experiment tests whether an…

Quantum Physics · Physics 2025-05-27 Peter Renkel

Quantum measurement finds the observed system in a collapsed state, rather than in the state predicted by the Schr\"odinger equation. Yet there is a relatively spread opinion that the wavefunction collapse can be explained by unitary…

Quantum Physics · Physics 2016-02-08 Ovidiu Cristinel Stoica

Time-symmetric cosmological theories, in which the initial and final states are arranged to have similar features or are independently fixed, have been quite extensively discussed in the literature. However, a more general and perhaps more…

General Relativity and Quantum Cosmology · Physics 2012-04-20 Adrian Kent

We consider a special form of state discrimination in which after the measurement we are given additional information that may help us identify the state. This task plays a central role in the analysis of quantum cryptographic protocols in…

Quantum Physics · Physics 2011-05-02 Deepthi Gopal , Stephanie Wehner

The quantum state discrimination problem is to distinguish between non-orthogonal quantum states. This problem has many applications in quantum information theory, quantum communication and quantum cryptography. In this paper a quantum…

Quantum Physics · Physics 2021-02-25 Doha A. Rizk , Ahmed Younes

The capabilities of a new approach towards the foundations of Statistical Mechanics are explored. The approach is genuine quantum in the sense that statistical behavior is a consequence of objective quantum uncertainties due to entanglement…

Quantum Physics · Physics 2010-03-29 Christian Gogolin

State smoothing is a technique to estimate a state at a particular time, conditioned on information obtained both before (past) and after (future) that time. For a classical system, the smoothed state is a normalized product of the…

Quantum Physics · Physics 2024-04-04 Kiarn T. Laverick , Prahlad Warszawski , Areeya Chantasri , Howard M. Wiseman

With the recent surge of interest in quantum computation, it has become very important to develop clear experimental tests for ``quantum behavior'' in a system. This issue has been addressed in the past in the form of the inequalities due…

Quantum Physics · Physics 2007-05-23 Rusko Ruskov , Alexander N. Korotkov , Ari Mizel

Characterization of quantum systems from experimental data is a central problem in quantum science and technology. But which measurements should be used to gather data in the first place? While optimal measurement choices can be worked out…

Quantum Physics · Physics 2025-07-15 Jiaxin Huang , Yan Zhu , Giulio Chiribella , Ya-Dong Wu

A new approach to the problem of measurement in quantum mechanics is proposed. In this approach, the process of measurement is described in the Heisenberg picture and divided into two stages. The first stage is to transduce the measured…

Quantum Physics · Physics 2007-05-23 Masanao Ozawa

Weak value amplification and other postselection-based metrological protocols can enhance precision while estimating small parameters, outperforming postselection-free protocols. In general, these enhancements are largely constrained…

Quantum Physics · Physics 2023-05-24 Sourav Das , Subhrajit Modak , Manabendra Nath Bera

We introduce the post-processing preorder and equivalence relations for general measurements on a possibly infinite-dimensional general probabilistic theory described by an order unit Banach space $E$ with a Banach predual. We define the…

Functional Analysis · Mathematics 2020-04-09 Yui Kuramochi