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Quantum metrology exploits quantum mechanical effects to increase the precision of measurements of physical quantities. A wide variety of applications are currently being developed for scientific and technological purposes, however, most…

Quantum Physics · Physics 2026-02-16 B. J. Alexander , Ş. K. Özdemir , M. S. Tame

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

While quantum reality can be probed through measurements, the Two-State-Vector formalism (TSVF) reveals a subtler reality prevailing between measurements. Under special pre- and post-selections, odd physical values emerge. This unusual…

Quantum Physics · Physics 2018-11-13 Yakir Aharonov , Eliahu Cohen , Mordecai Waegell , Avshalom C. Elitzur

The quantum state of Schroedinger's cat is usually incorrectly described as a superposition of "dead" and "alive," despite an argument by Rinner and Werner that, locally, the cat should be considered to be in a mixture of non-superposed…

Quantum Physics · Physics 2022-06-14 Art Hobson

We address the problem of interference using the Heisenberg picture and highlight some new aspects through the use of pre-selection, post-selection, weak measurements, and modular variables, We present a physical explanation for the…

Quantum Physics · Physics 2015-05-14 Jeff Tollaksen , Yakir Aharonov , Aharon Casher , Tirzah Kaufherr , Shmuel Nussinov

Entanglement-enhanced quantum metrology explores the utilization of quantum entanglement to enhance measurement precision. When particles in a probe are prepared into a quantum entangled state, they collectively accumulate information about…

Quantum Physics · Physics 2024-08-20 Jiahao Huang , Min Zhuang , Chaohong Lee

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

The usual conjectures of quantum measurements approaches, inspired from the traditional interpretation of Heisenberg's ("uncertainty") relations, are proved as being incorrect. A group of reconsidered conjectures and a corresponding new…

Quantum Physics · Physics 2007-05-23 Spiridon Dumitru

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

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

Coherent superposition states of a mesoscopic quantum object play a major role in our understanding of the quantum to classical boundary, as well as in quantum-enhanced metrology and computing. However, their practical realization and…

We investigate the superposition of coherent states, emphasizing quantum states with distinct Wigner phase-space features relevant to quantum information applications. In this study, we introduce generalized versions of the compass state,…

Quantum Physics · Physics 2025-08-26 Tan Hailin , Naeem Akhtar , Gao Xianlong

Weak measurements performed between quantum state preparation and post-selection result in complex values for self-adjoint operators, corresponding to complex conditional probabilities for the projections on specific eigenstates. In this…

Quantum Physics · Physics 2011-10-14 Holger F. Hofmann

Pure states are usually used to observe quantum phenomena. In this study, we show that a quantum superposition of spatially displaced mixed cat states can be generated within an optical waveguide via nonparaxial unitary evolution of the…

Quantum Physics · Physics 2025-12-01 N. I. Petrov

Spin cat states are promising candidates for quantum-enhanced measurement. Here, we analytically show that the ultimate measurement precision of spin cat states approaches the Heisenberg limit, where the uncertainty is inversely…

Quantum Physics · Physics 2018-07-25 Jiahao Huang , Min Zhuang , Bo Lu , Yongguan Ke , Chaohong Lee

We investigate the utility of non classical states of simple harmonic oscillators, particularly a superposition of coherent states, for sensitive force detection. We find that like squeezed states a superposition of coherent states allows…

Quantum Physics · Physics 2009-11-07 W. J. Munro , K. Nemoto , G. J. Milburn , S. L. Braunstein

In quantum phase estimation, the Heisenberg limit provides the ultimate accuracy over quasi-classical estimation procedures. However, realizing this limit hinges upon both the detection strategy employed for output measurements and the…

Quantum Physics · Physics 2024-07-23 Hanan Saidi , Hanane El Hadfi , Abdallah Slaoui , Rachid Ahl Laamara

A many-body atomic system coupled to quantized light is subject to weak measurement. Instead of coupling light to the on-site density, we consider the quantum backaction due to the measurement of matter-phase-related variables such as…

Quantum Physics · Physics 2017-02-27 Wojciech Kozlowski , Santiago F. Caballero-Benitez , Igor B. Mekhov

We outline a toolbox comprised of passive optical elements, single photon detection and superpositions of coherent states (Schrodinger cat states). Such a toolbox is a powerful collection of primitives for quantum information processing…

Quantum Physics · Physics 2009-11-10 A. Gilchrist , Kae Nemoto , W. J. Munro , T. C. Ralph , S. Glancy , Samuel. L. Braunstein , G. J. Milburn

Hyperentanglement --- simultaneous entanglement between multiple degrees of freedom of two or more systems --- has been used to enhance quantum information tasks such as quantum communication and photonic quantum computing. Here we show…

Quantum Physics · Physics 2018-01-17 S. P. Walborn , A. H. Pimentel , L. Davidovich , R. L. de Matos Filho