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Experimentally, the imaginary parts of complex weak values are obtained from the response of the system to small unitary phase shifts generated by the target observable. The complex conditional probabilities obtained from weak measurements…

Quantum Physics · Physics 2011-05-03 Holger F. Hofmann

By generalizing the quantum weak measurement protocol to the case of quantum fields, we show that weak measurements probe an effective classical background field that describes the average field configuration in the spacetime region between…

Quantum Physics · Physics 2014-03-24 Justin Dressel , Konstantin Y. Bliokh , Franco Nori

An unstable quantum state generally decays following an exponential law, as environmental decoherence is expected to prevent the decay products from recombining to reconstruct the initial state. Here we show the existence of deviations from…

Quantum Physics · Physics 2017-10-02 M. Beau , J. Kiukas , I. L. Egusquiza , A. del Campo

Weak values are average quantities,therefore investigating their associated variance is crucial in understanding their place in quantum mechanics. We develop the concept of a position-postselected weak variance of momentum as cohesively as…

Quantum Physics · Physics 2015-08-10 M. R. Feyereisen

Post-inflationary boundary conditions are essential to the existence of our highly structured universe, and these can only come about through quantum mechanical state reductions - i.e., through measurements. The choice is between: An…

Quantum Physics · Physics 2007-05-23 Richard A Mould

An analysis of errors in measurement yields new insight into classically forbidden quantum processes. In addition to "physical" values, a realistic measurement can yield "unphysical" values; we show that in {\it sequences} of measurements,…

Condensed Matter · Physics 2009-10-22 Daniel Rohrlich , Yakir Aharonov , Sandu Popescu , Lev Vaidman

Svensson [Found. Phys. 45, 1645 (2015)] argued that the concept of the weak value of an observable of a pre- and post-selected quantum system cannot be applied when the expectation value of the observable in the initial state vanishes.…

Quantum Physics · Physics 2022-10-12 Alon Ben Israel , L. Vaidman

An example shows that weak decoherence is more restrictive than the minimal logical decoherence structure that allows probabilities to be used consistently for quantum histories. The probabilities in the sum rules that define minimal…

Quantum Physics · Physics 2010-10-11 Thomas F. Jordan , Eric D. Chisolm

Quantum nonlocality offers a secure way to produce random numbers: their unpredictability is intrinsic and can be certified just by observing the statistic of the measurement outcomes, without assumptions on how they are produced. To do…

Weak measurements of photon position can be used to obtain direct experimental evidence of the wavefunction of a photon between generation and ultimate detection. Significantly, these measurement results can also be understood as complex…

Quantum Physics · Physics 2014-06-11 Holger F. Hofmann

An EPR experiment is studied where each particle within the entangled pair undergoes a few weak measurements (WMs) along some pre-set spin orientations, with the outcomes individually recorded. Then the particle undergoes one strong…

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

We extend the idea of weak measurements to the general case, provide a complete treatment and obtain results for both the regime when the pre-selected and post-selected states (PPS) are almost orthogonal and the regime when they are exactly…

Quantum Physics · Physics 2015-03-17 Shengjun Wu , Yang Li

It is often said that measuring a system's position must disturb the complementary property, momentum, by some minimum amount due to the Heisenberg uncertainty principle. Using a "weak-measurement", this disturbance can be reduced. One…

Quantum Physics · Physics 2018-11-26 G. S. Thekkadath , F. Hufnagel , J. S. Lundeen

From the analysis of the relaxation process of isolated lattice many-body quantum systems quenched far from equilibrium, we deduce a criterion for predicting when they are certain to thermalize. It is based on the algebraic behavior…

Statistical Mechanics · Physics 2017-01-27 Marco Távora , E. J. Torres-Herrera , Lea F. Santos

In this work we establish a link between two apparently unrelated subjects: polarization effects in optical fibers and devices, and the quantum theory of weak measurements. We show that the abstract concept of weak measurements followed by…

Quantum Physics · Physics 2007-05-23 Nicolas Brunner

The variance of an observable in a pre-selected quantum system, which is always real and non-negative, appears as an increase in the probe wave packet width in indirect measurements. Extending this framework to pre- and post-selected…

Quantum Physics · Physics 2021-07-28 Kazuhisa Ogawa , Natsuki Abe , Hirokazu Kobayashi , Akihisa Tomita

What happens when a quantum system undergoing unitary evolution in time is subject to repeated projective measurements to the initial state at random times? A question of general interest is: How does the survival probability $S_m$, namely,…

Quantum Physics · Physics 2022-04-01 Debraj Das , Shamik Gupta

Time averaging of weak values using the quantum transition path time probability distribution enables us to establish a general uncertainty principle for the weak values of two not necessarily Hermitian operators. This new principle is a…

Quantum Physics · Physics 2019-01-16 Eli Pollak , Salvador Miret-Artés

We show that the phenomenon of anomalous weak values is not limited to quantum theory. In particular, we show that the same features occur in a simple model of a coin subject to a form of classical backaction with pre- and post-selection.…

Quantum Physics · Physics 2014-09-19 Christopher Ferrie , Joshua Combes

Many seemingly paradoxical effects are known in the predictions for outcomes of intermediate measurements made on pre- and post-selected quantum systems. Despite appearances, these effects do not demonstrate the impossibility of a…

Quantum Physics · Physics 2007-05-23 M. S. Leifer , R. W. Spekkens