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Weak measurements are a new tool for characterizing post-selected quantum systems during their evolution. Weak measurement was originally formulated in terms of von Neumann interactions which are practically available for only the simplest…

Quantum Physics · Physics 2009-11-11 J. S. Lundeen , K. J. Resch

In quantum theory, a weak value is a complex number with a somewhat technical definition: it is a ratio whose numerator is the matrix element of a self-adjoint operator and whose denominator is the inner product of a corresponding pair of…

Quantum Physics · Physics 2026-02-11 Jacob A. Barandes

In the weak measurement formalism of Y. Aharonov et al. the so-called weak value A_w of any observable A is generally a complex number. We derive a physical interpretation of its value in terms of the shift in the measurement pointer's mean…

Quantum Physics · Physics 2009-11-13 Richard Jozsa

Weak measurements can be seen as an attempt at answering the 'Which way?' question without destroying interference between the pathways involved. Unusual mean values obtained in such measurements represent the response of a quantum system…

Quantum Physics · Physics 2013-05-27 D. Sokolovski

Weak measurement is unique in enabling measurements of non-commuting operators as well as otherwise-undetectable peculiar phenomena predicted by the Two-State-Vector-Formalism (TSVF). This article, the first in two parts, explores novel…

Quantum Physics · Physics 2015-06-23 Yakir Aharonov , Eliahu Cohen , Avshalom C. Elitzur

We propose an experiment which demonstrates the undoing of a weak continuous measurement of a solid-state qubit, so that any unknown initial state is fully restored. The undoing procedure has only a finite probability of success because of…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Alexander N. Korotkov , Andrew N. Jordan

The operational definition of a weak value for a quantum mechanical system involves the limit of the weak measurement strength tending to zero. I study how this limit compares to the situation for the undisturbed (no weak measurement)…

Quantum Physics · Physics 2015-10-26 B. E. Y. Svensson

We address continuous weak linear quantum measurement and argue that it is best understood in terms of statistics of the outcomes of the linear detectors measuring a quantum system, for example, a qubit. We mostly concentrate on a setup…

Mesoscale and Nanoscale Physics · Physics 2008-07-14 Hongduo Wei , Yuli V. Nazarov

We discuss whether, to what extent and how a quantum computing device can be evaluated and simulated using classical tools.

We extend the definition of quantum discord as a quantifier of nonClassical correlations in a quantum state to the case where weak measurements are performed on subsystem $A$ of a bipartite system $AB$. The properties of weak discord are…

Quantum Physics · Physics 2015-12-01 Lekshmi S , N Shaji , Anil Shaji

Weak values and measurements have been proposed as means to achieve dramatic enhancements in metrology based on the greatly increased range of possible measurement outcomes. Unfortunately, the very large values of measurement outcomes occur…

Quantum Physics · Physics 2015-06-02 Lijian Zhang , Animesh Datta , Ian A. Walmsley

We demonstrate the conditional reversal of a weak (partial-collapse) quantum measurement on a photonic qubit. The weak quantum measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state…

Quantum Physics · Physics 2015-05-13 Yong-Su Kim , Young-Wook Cho , Young-Sik Ra , Yoon-Ho Kim

One of the most intriguing aspects of Quantum Mechanics is the impossibility of measuring at the same time observables corresponding to non-commuting operators. This impossibility can be partially relaxed when considering joint or…

A weak measurement consists in coupling a system to a probe in such a way that constructive interference generates a large output. So far, only the average output of the probe and its variance were studied. Here, the characteristic function…

Quantum Physics · Physics 2012-03-07 Antonio Di Lorenzo

The weak value, introduced by Aharonov et al. to extend the conventional scope of physical observables in quantum mechanics, is an intriguing concept which sheds new light on quantum foundations and is also useful for precision measurement,…

Quantum Physics · Physics 2014-10-06 Takuya Mori , Izumi Tsutsui

This paper establishes a direct, robust and intimate connection between (i) non classicality tests for various quantum features, e.g., non-Boolean logic, quantum coherence, nonlocality, quantum entanglement, quantum discord; (ii) negative…

Quantum Physics · Physics 2021-10-26 Sooryansh Asthana , V. Ravishankar

A quantum transition can be seen as a result of interference between various pathways(e.g. Feynman paths) which can be labelled by a variable $f$. An attempt to determine the value of f without destroying the coherence between the pathways…

Quantum Physics · Physics 2009-05-26 D. Sokolovski

Quantum computers are on the brink of surpassing the capabilities of even the most powerful classical computers. This naturally raises the question of how one can trust the results of a quantum computer when they cannot be compared to…

The fact that not all quantum observables are jointly measurable is one of the major differences between quantum and classical theory. In the former, non-commuting observables can only be simultaneously measured with limited precision. We…

Quantum Physics · Physics 2016-10-17 Gilles Pütz , Tomer Barnea , Nicolas Gisin , Anthony Martin

We review the definition and the concepts of the weak values and some measurement model to extract the weak value. This material is based on the author Ph.D. thesis "Time in Weak Values and Discrete Time Quantum Walk" at Tokyo Institute of…

Quantum Physics · Physics 2021-07-19 Yutaka Shikano