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We revisit the problem of preparing a mechanical oscillator in the vicinity of its quantum-mechanical ground state by means of feedback cooling based on continuous optical detection of the oscillator position. In the parameter regime…

Quantum Physics · Physics 2016-08-18 Hojat Habibi , Emil Zeuthen , Majid Ghanaatshoar , Klemens Hammerer

Projective (Von Neumann) Measurement of an operator (i.e. a dynamical variable) selected from a prescribed set of operators is termed unrecorded measurement (URM) when both the selected operator and the measurement outcome are unknown, i.e.…

Quantum Physics · Physics 2016-09-21 M. Revzen , A. Mann

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

The notion of weak measurement provides a formalism for extracting information from a quantum system in the limit of vanishing disturbance to its state. Here we extend this formalism to the measurement of sequences of observables. When…

Quantum Physics · Physics 2009-11-13 Graeme Mitchison , Richard Jozsa , Sandu Popescu

Recently, weak measurements have attracted a lot of interest as an experimental method for the investigation of non-classical correlations between observables that cannot be measured jointly. Here, I explain how the complex valued…

Quantum Physics · Physics 2013-05-02 Holger F. Hofmann

We investigate the process of quantum measurements on scattered probes. Before scattering, the probes are independent, but they become entangled afterwards, due to the interaction with the scatterer. The collection of measurement results…

Mathematical Physics · Physics 2015-03-23 Marco Merkli , Mark Penney

The entanglement of multi-atom quantum states is considered. In order to cancel noise due to inhomogeneous light atom coupling, the concept of matched multi-atom observables is proposed. As a means to eliminate an important form of…

Quantum Physics · Physics 2009-11-10 A. Kuzmich , T. A. B. Kennedy

We propose a machine learning-based approach enhanced by quantum reservoir computing (QRC) to estimate the zero-time second-order correlation function g2(0). Typically, measuring g2(0) requires single-photon detectors and time-correlated…

Quantum Physics · Physics 2025-04-28 Dogyun Ko , Stanisław Świerczewski , Andrzej Opala , Michał Matuszewski , Amir Rahmani

Out-of-time-order correlator (OTOC), been suggested as a measure of quantum information scrambling in quantum many-body systems, has received enormous attention recently. The experimental measurement of OTOC is quite challenging. The…

Quantum Physics · Physics 2019-04-01 Xinfang Nie , Ze Zhang , Xiuzhu Zhao , Tao Xin , Dawei Lu , Jun Li

The origin of non-classicality in physical systems and its connection to distinctly quantum features such as entanglement and coherence is a central question in quantum physics. This work analyses this question theoretically and…

In quantum physics, all measured observables are subject to statistical uncertainties, which arise from the quantum nature as well as the experimental technique. We consider the statistical uncertainty of the so-called sampling method, in…

Quantum Physics · Physics 2012-06-08 Thomas Kiesel

Measurements done on the quantum systems are too specific. Contrary to their classical counterparts, quantum measurements can be invasive and destroy the state of interest. Besides, quantumness limits the accuracy of measurements done on…

Measurement incompatibility is one of the most striking examples of how quantum physics is different from classical physics. Two measurements are incompatible if they cannot arise via classical post-processing from a third one. A natural…

Quantum Physics · Physics 2022-11-21 Andreas Bluhm , Ion Nechita

A new operator based condition for distinguishing classical from non-classical states of quantised radiation is developed. It exploits the fact that the normal ordering rule of correspondence to go from classical to quantum dynamical…

Quantum Physics · Physics 2008-11-26 Arvind , N. Mukunda , R. Simon

In [Berta 2014 Entanglement], uncertainty relations in the presence of quantum memory was formulated for mutually unbiased bases using conditional collision entropy. In this paper, we generalize their results to the mutually unbiased…

Quantum Physics · Physics 2018-10-03 Kun Wang , Nan Wu , Fangmin Song

Measurement incompatibility has proved to be an important resource for quantum information processing. In this work, we present an operational approach that leverages classical operations on the inputs (pre-processing) and outputs…

Quantum Physics · Physics 2026-01-16 Arun Kumar Das , Saheli Mukherjee , Debashis Saha , Debarshi Das , A. S. Majumdar

We show that the recently discovered quantum-enhanced measurement protocol of coherent averaging that is capable of achieving Heisenberg-limited sensitivity without using entanglement, has a classical analogue. The classical protocol uses N…

Quantum Physics · Physics 2013-05-07 Daniel Braun , Sandu Popescu

Charge detection utilizing a highly biased quantum point contact has become the most effective probe for studying few electron quantum dot circuits. Measurements on double and triple quantum dot circuits is performed to clarify a back…

Mesoscale and Nanoscale Physics · Physics 2008-05-04 D. Taubert , M. Pioro-Ladrière , D. Schröer , D. Harbusch , A. S. Sachrajda , S. Ludwig

Incoherence in the controlled Hamiltonian is an important limitation on the precision of coherent control in quantum information processing. Incoherence can typically be modelled as a distribution of unitary processes arising from slowly…

Quantum Physics · Physics 2009-11-10 N. Boulant , S. Furuta , J. Emerson , T. F. Havel , D. G. Cory

The recent development of single-atom-resolved probes has made full counting statistics measurements accessible in quantum gas experiments. This capability provides access to high-order moments of physical observables, from which cumulants,…