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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

We prove uncertainty relations that quantitatively express the impossibility of jointly sharp preparation of pre- and post-selected quantum states for measuring incompatible observables during the weak measurement. By defining a suitable…

Quantum Physics · Physics 2014-11-27 Arun Kumar Pati , Junde Wu

We quantify the disturbance of a quantum state undergoing a sequence of observations, and particularly focus on a weak measurement followed by post-selection and compare these results to the projective counterpart. Taking into account the…

Quantum Physics · Physics 2021-01-04 Philipp Stammer

We explore further the suggestion to describe a pre- and post-selected system by a two-state, which is determined by two conditions. Starting with a formal definition of a two-state Hilbert space and basic operations, we systematically…

Quantum Physics · Physics 2009-10-28 B. Reznik , Y. Aharonov

This paper starts with a brief review of the topic of strong and weak pre- and post-selected (PPS) quantum measurements, as well as weak values, and afterwards presents original work. In particular, we develop a nonperturbative theory of…

Quantum Physics · Physics 2012-10-16 Abraham G. Kofman , Sahel Ashhab , Franco Nori

Quantum measurement is physically realized through a finite dynamical interaction between a system and a measuring apparatus, giving rise to a continuous transition from weak to strong regimes. While this crossover is well understood under…

Traditional uncertainty relations dictate a minimal amount of noise in incompatible projective quantum measurements. However, not all measurements are projective. Weak measurements are minimally invasive methods for obtaining partial state…

Quantum Physics · Physics 2021-03-15 Jonathan T. Monroe , Nicole Yunger Halpern , Taeho Lee , Kater W. Murch

Spontaneous symmetry breaking (SSB) is the cornerstone of our understanding of quantum phases of matter. Recent works have generalized this concept to the domain of mixed states in open quantum systems, where symmetries can be realized in…

Quantum Physics · Physics 2025-12-30 Xiaozhou Feng , Zihan Cheng , Matteo Ippoliti

A weak measurement performed on a pre- and post-selected quantum system can result in an average value that lies outside of the observable's spectrum. This effect, usually referred to as an "anomalous weak value", is generally believed to…

Quantum Physics · Physics 2019-10-16 Alastair A. Abbott , Ralph Silva , Julian Wechs , Nicolas Brunner , Cyril Branciard

The reconstruction of quantum states from a sufficient set of experimental data can be achieved with arbitrarily weak measurement interactions. Since such weak measurements have negligible back-action, the quantum state reconstruction is…

Quantum Physics · Physics 2010-03-16 Holger F. Hofmann

This work will incorporate a few related tools for addressing the conceptual difficulties arising from sewing together classical and quantum mechanics: deterministic operators, weak measurements and post-selection. Weak Measurement, based…

Quantum Physics · Physics 2016-12-21 Eliahu Cohen , Yakir Aharonov

The article recapitulates the concept of weak measurement in its broader sense encapsulating the trade between asymptotically weak measurement precision and asymptotically large measurement statistics. Essential applications in…

Quantum Physics · Physics 2007-05-23 Lajos Diosi

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

It is well known that the pointer state |{\Phi}> resulting from the von Neumann measurement of a projection operator A performed upon an ensemble of quantum systems in the preselected state |{\psi}> depends upon A|{\psi}>. Here it is shown…

Quantum Physics · Physics 2012-08-07 A. D. Parks , J. E. Gray

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

Weak value is increasingly acknowledged as an important research tool for probing quantum pre- and post-selected ensembles, where some extraordinary phenomena occur. We generalize this concept to the broader notion of "weak potential" which…

Quantum Physics · Physics 2013-01-14 Yakir Aharonov , Eliahu Cohen , Shay Ben-Moshe

The weak values and weak measurement formalism were initially limited to pure states, which were later extended to mixed states, leading to intriguing applications in quantum information processing tasks. Weak values are considered to be…

Quantum Physics · Physics 2025-11-04 Rajendra Singh Bhati

When the weak value of a projector is 1, a quantum system behaves as in that eigenstate with probability 1. By definition, however, the weak value may take an anomalous value lying outside the range of probability like -1. From the…

Quantum Physics · Physics 2016-12-21 Kazuhiro Yokota , Nobuyuki Imoto

Weak measurements have an increasing number of applications in contemporary quantum mechanics. They were originally described as a weak interaction that slightly entangled the translational degrees of freedom of a particle to its spin,…

Weak values are the fundamental values for observables in a pre- and post-selected system. Weak values are typically measured by weak measurement, in which weak values appear in the change of not the pre- and post-selected system but the…

Quantum Physics · Physics 2020-04-21 Kazuhisa Ogawa , Hirokazu Kobayashi , Akihisa Tomita