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We investigate the sequential composition of weak values in the framework of time-symmetric quantum mechanics. Specifically, we consider a forward'' weak measurement from a preselected state $\ket{\psi}$ to a post-selected state…

Quantum Physics · Physics 2025-07-15 Mirco A. Mannucci

The readings of a highly inaccurate "weak" quantum meter, employed to determine the value of a dichotomous variable $S$ without destroying the interference between the alternatives,may take arbitrary values. We show that the expected values…

Quantum Physics · Physics 2015-09-17 D. Sokolovski

We discuss the preceding Comment and conclude that the arguments given there against the relevance of null weak values as representing the absence of a system property are not compelling. We give an example in which the transition matrix…

Quantum Physics · Physics 2018-04-18 Q. Duprey , A. Matzkin

We address the issue of how to properly treat, and in a more general setting, the concept of a weak value of a weak measurement in quantum mechanics. We show that for this purpose, one must take in account the effects of the measuring…

Quantum Physics · Physics 2009-07-24 A. C. Lobo , C. A. Ribeiro

We generalize the concept of a weak value of a quantum observable to cover arbitrary real positive operator measures. We show that the definition is operationally meaningful in the sense that it can be understood within the quantum theory…

Quantum Physics · Physics 2013-05-29 Erkka Haapasalo , Pekka Lahti , Jussi Schultz

Weak measurements in combination with post-selection can give rise to a striking amplification effect (related to a large "weak value"). We show that this effect can be understood by viewing the initial state of the pointer as the ground…

Quantum Physics · Physics 2015-05-20 Christoph Simon , Eugene S. Polzik

We experimentally determine weak values for a single photon's polarization, obtained via a weak measurement that employs a two-photon entangling operation, and postselection. The weak values cannot be explained by a semiclassical wave…

Quantum Physics · Physics 2008-11-26 G. J. Pryde , J. L. O'Brien , A. G. White , T. C. Ralph , H. M. Wiseman

Is it possible that a measurement of a spin component of a spin-1/2 particle yields the value 100? In 1988 Aharonov, Albert and Vaidman argued that upon pre- and postselection of particular spin states, weakening the coupling of a standard…

Quantum measurement is one of the most fascinating and discussed phenomena in quantum physics, due to the impact on the system of the measurement action and the resulting interpretation issues. Scholars proposed weak measurements to amplify…

Quantum Physics · Physics 2024-01-23 Lorena Ballesteros Ferraz , Riccardo Muolo , Yves Caudano , Timoteo Carletti

Conventional quantum mechanics describes a pre- and post-selected system in terms of virtual (Feynman) paths via which the final state can be reached. In the absence of probabilities, a weak measurement (WM) determines the probability…

Quantum Physics · Physics 2016-04-20 D. Sokolovski

An experimental proposal is presented in which dark port post-selection together with weak measurements are used to enlarge the radiation pressure effect of a single photon on a mechanical oscillator placed in the middle of a Fabry-Perot…

Quantum Physics · Physics 2019-01-09 Sergio Carrasco , Miguel Orszag

Since its introduction 25 years ago, the quantum weak value has gradually transitioned from a theoretical curiosity to a practical laboratory tool. While its utility is apparent in the recent explosion of weak value experiments, its…

Quantum Physics · Physics 2014-04-02 Justin Dressel , Mehul Malik , Filippo M. Miatto , Andrew N. Jordan , Robert W. Boyd

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

We re-examine the status of the weak value of a quantum mechanical observable as an objective physical concept, addressing its physical interpretation and general domain of applicability. We show that the weak value can be regarded as a…

Quantum Physics · Physics 2007-05-23 Yakir Aharonov , Alonso Botero

The real part of the weak value is identified as the conditional Bayes probability through the quantum analog of the Bayes relation. We present an explicit protocol to get the the weak values in a simple Mach-Zehnder interferometer model…

Quantum Physics · Physics 2015-09-25 Akio Hosoya

Quantum measurements can be generalized to include complex quantities. It is possible to relate the quantum weak values of projection operators to the third order Bargmann invariants. The argument of the weak value becomes, up to a sign,…

Quantum Physics · Physics 2021-09-22 Z. Gedik

Uncertainty principle forbids one to determine which of the two paths a quantum system has travelled, unless interference between the alternatives had been destroyed by a measuring device, e.g., by a pointer. One can try to weaken the…

Quantum Physics · Physics 2025-03-18 A. Uranga , E. Akhmatskaya , D. Sokolovski

We discuss two questions related to the concept of weak values as seen from the standard quantum-mechanics point of view. In the first part of the paper, we describe a scenario where unphysical results similar to those encountered in the…

Quantum Physics · Physics 2009-07-29 S. Ashhab , Franco Nori

We study the weak values of a quantum observable from the point of view of the Wigner formalism. The main actor is here the cross-Wigner transform of two functions, which is in disguise the cross-ambiguity function familiar from radar…

Quantum Physics · Physics 2015-05-30 Maurice A. de Gosson , Serge M. de Gosson

Weak values arise in quantum theory when the result of a weak measurement is conditioned on a subsequent strong measurement. The majority of the trials are discarded, leaving only very few successful events. Intriguingly those can display a…

Quantum Physics · Physics 2016-05-19 George C. Knee , Joshua Combes , Christopher Ferrie , Erik M. Gauger