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We establish a framework for realizing back-action-evading (BAE) measurements and quantum non-demolition (QND) variables in linear quantum systems. The key condition, a purely imaginary Hamiltonian with a real or imaginary coupling…

Quantum Physics · Physics 2026-04-28 Zhiyuan Dong , Weichao Liang , Guofeng Zhang

We address measurement-based generation of quantum coherence in continuous variable systems. We consider Gaussian measurements performed on Gaussian states and focus on two scenarios. In the first one, we assume an initially correlated…

Quantum Physics · Physics 2017-08-14 Francesco Albarelli , Marco G. Genoni , Matteo G. A. Paris

We use quantum entanglement witnesses derived from Gaussian operators to study the separable criteria of continuous variable states. We transform the validity of a Gaussian witness to a Bosonic Gaussian channel problem. It follows that the…

Quantum Physics · Physics 2022-08-29 Xiao-yu Chen , Maoke Miao , Rui Yin , Jiantao Yuan

Quantum correlations in a composite system can be measured by resorting to a geometric approach, according to which the distance from the state of the system to a suitable set of classically correlated states is considered. Here we show…

Quantum Physics · Physics 2015-06-10 Marco Cianciaruso , Thomas R. Bromley , Wojciech Roga , Rosario Lo Franco , Gerardo Adesso

We provide a unified framework for nonsignalling quantum and classical multipartite correlations, allowing all to be written as the trace of some local (quantum) measurements multiplied by an operator. The properties of this operator define…

Quantum Physics · Physics 2013-05-29 A. Acín , R. Augusiak , D. Cavalcanti , C. Hadley , J. K. Korbicz , M. Lewenstein , Ll. Masanes , M. Piani

Determining when the multiparameter quantum Cram\'er--Rao bound (QCRB) is saturable with experimentally relevant single-copy measurements is a central open problem in quantum metrology. Here we establish an equivalence between QCRB…

Quantum Physics · Physics 2026-01-30 Jing Yang , Satoya Imai , Luca Pezzè

Quantum correlations in Bell and prepare-and-measure experiments are central resources for probing nonclassicality and enabling device-based quantum information protocols. In the absence of shared public randomness (i.e., without run-to-run…

Quantum Physics · Physics 2026-04-21 Liang-Liang Sun , Xiang Zhou , Chengjie Zhang , Zizhu Wang , Yong-Shun Song , Sixia Yu

No physical measurement can be performed with infinite precision. This leaves a loophole in the standard no-go arguments against non-contextual hidden variables. All such arguments rely on choosing special sets of quantum-mechanical…

Quantum Physics · Physics 2009-10-31 Rob Clifton , Adrian Kent

We investigate the effect of conditional null measurements on a quantum system and find a rich variety of behaviors. Specifically, quantum dynamics with a time independent $H$ in a finite dimensional Hilbert space are considered with…

Quantum Physics · Physics 2022-06-20 Quancheng Liu , Klaus Ziegler , David A. Kessler , Eli Barkai

Deficit of information zero-way was proposed in HorodeckiHHOSSS2005 as one of possible measures of quantumness of correlations. Numerical calculations suggested that there exist such states for which this quantity is almost equal to mutual…

Quantum Physics · Physics 2008-02-12 Łukasz Pankowski , Barbara Synak-Radtke

It is known that quantum correlations exhibited by a maximally entangled qubit pair can be simulated with the help of shared randomness, supplemented with additional resources, such as communication, post-selection or non-local boxes. For…

Quantum Physics · Physics 2009-11-11 Julien Degorre , Sophie Laplante , Jérémie Roland

We propose a measure of non-Gaussianity for quantum states of a system of $n$ oscillator modes. Our measure is based on the quasi-probability $Q(\alpha), \alpha\in{\cal C}^n$. Since any measure of non-Gaussianity is necessarily an attempt…

Quantum Physics · Physics 2008-12-16 J. Solomon Ivan , M. Sanjay Kumar , R. Simon

We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number using a single electron transistor (SET). The measurement is made when the bare tunneling…

Mesoscale and Nanoscale Physics · Physics 2019-08-17 H. M. Wiseman , Dian Wahyu Utami , He Bi Sun , G. J. Milburn , B. E. Kane , A. Dzurak , R. G. Clark

We investigate whether paradigmatic measurements for quantum state tomography, namely mutually unbiased bases and symmetric informationally complete measurements, can be employed to certify quantum correlations. For this purpose, we…

Quantum steering describes the ability of one observer to nonlocally affect the other observer's state through local measurements, which represents a new form of quantum nonlocal correlation and has potential applications in quantum…

Quantum Physics · Physics 2020-10-06 Guo-Zhu Pan , Jun-Long Zhao , Zhi Lin , Ming Yang , Gang Zhang , Zhuo-Liang Cao

We consider how to quantify non-Gaussianity for the correlation of a bipartite quantum state by using various measures such as relative entropy and geometric distances. We first show that an intuitive approach, i.e., subtracting the…

Quantum Physics · Physics 2017-11-21 Jiyong Park , Jaehak Lee , Se-Wan Ji , Hyunchul Nha

A key lesson of the decoherence program is that information flowing out from an open system is stored in the quantum state of the surroundings. Simultaneously, quantum measurement theory shows that the evolution of any open system when its…

Quantum Physics · Physics 2012-01-27 Juan Diego Urbina , Walter T. Strunz , Carlos Viviescas

A general and computable criterion for k-(in)separability in continuous multipartite quantum systems is presented. The criterion can be experimentally implemented with a finite and comparatively low number of local observables. We discuss…

Quantum Physics · Physics 2012-02-07 Andreas Gabriel , Marcus Huber , Sasa Radic , Beatrix C. Hiesmayr

Establishing a notion of the quantum state that applies consistently across space and time could be a crucial step toward formulating a relativistic quantum theory. We give an operational meaning to multipartite quantum states over…

Quantum Physics · Physics 2026-04-14 Seok Hyung Lie , Hyukjoon Kwon

Consider the question: what statistical ensemble corresponds to minimal prior knowledge about a quantum system ? For the case where the system is in fact known to be in a pure state there is an obvious answer, corresponding to the unique…

Quantum Physics · Physics 2009-10-31 Michael J. W. Hall