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In quantum metrology, the parameter estimation accuracy is bounded by quantum Fisher information. In this paper, we present coherence measures in terms of (quantum) Fisher information by directly considering the post-selective non-unitary…

Quantum Physics · Physics 2023-07-06 Deng-hui Yu , Chang-shui Yu

A pair of quantum observables diagonal in the same "incoherent" basis can be measured jointly, so some coherence is obviously required for measurement incompatibility. Here we first observe that coherence in a single observable is linked to…

Quantum Physics · Physics 2022-01-11 Jukka Kiukas , Daniel McNulty , Juha-Pekka Pellonpää

Coherence and correlations represent two related properties of a compound system. The system can be, for instance, the polarization of a photon, which forms part of a polarization-entangled two-photon state, or the spatial shape of a…

Quantum Physics · Physics 2015-12-01 Jiří Svozilík , Adam Vallés , Jan Peřina , Juan P. Torres

In this paper we investigate the robustness of the quantum correlations against the environment effects in various opto-mechanical bipartite systems. For two spatially separated opto-mechanical cavities, we give analytical formula for the…

Quantum Physics · Physics 2015-12-09 J. El Qars , M. Daoud , Ahl Laamara

The concept of coherence is one of cornerstones in physics. The development of quantum information science has lead to renewed interest in properly approaching the coherence at the quantum level. Various measures could be proposed to…

Quantum Physics · Physics 2016-04-06 Alexey E. Rastegin

We investigate in detail a recently introduced "coherent averaging scheme" in terms of its usefulness for achieving Heisenberg limited sensitivity in the measurement of different parameters. In the scheme, $N$ quantum probes in a product…

Quantum Physics · Physics 2023-07-19 Julien M. E. Fraïsse , Daniel Braun

We report the experimental measurement of bipartite quantum correlations of an unknown two-qubit state. Using a liquid state Nuclear Magnetic Resonance (NMR) setup and employing geometric discord, we evaluate the quantum correlations of a…

Based on the theory of quantum mechanics, intrinsic randomness in measurement distinguishes quantum effects from classical ones. From the perspective of states, this quantum feature can be summarized as coherence or superposition in a…

Quantum Physics · Physics 2017-04-03 Xiao Yuan , Hongyi Zhou , Zhu Cao , Xiongfeng Ma

Relevance of key quantum information measures for analysis of quantum systems is discussed. It is argued that possible ways of measuring quantum information are based on compatibility/incompatibility of the quantum states of a quantum…

Quantum Physics · Physics 2015-06-26 B. A. Grishanin , V. N. Zadkov

We study the ability of a quantum channel to generate quantum coherence when it applies to incoherent states. We define the measure of coherence generating power (CGP) for a generic quantum channel to be the average coherence generated by…

Quantum Physics · Physics 2022-07-05 Zhaoqi Wu , Lin Zhang , Shao-Ming Fei , Jianhui Wang

Although quantum coherence is a basic trait of quantum mechanics, the presence of coherences in the quantum description of a certain phenomenon does not rule out the possibility to give an alternative description of the same phenomenon in…

Quantum Physics · Physics 2018-12-07 Andrea Smirne , Dario Egloff , María García Díaz , Martin B. Plenio , Susana F. Huelga

It is shown that a choice of degrees of freedom of a bipartite continuous variable system determines amount of non-classical correlations (quantified by discord) in the system's state. Non-classical correlations (that include entanglement…

Quantum Physics · Physics 2013-04-01 M. Dugic , M. Arsenijevic , J. Jeknic-Dugic

Quantum coherence with respect to orthonormal bases has been studied extensively in the past few years. Recently, Bischof, et al. [Phys. Rev. Lett. 123, 110402 (2019)] generalized it to the case of general positive operator-valued measure…

Quantum Physics · Physics 2020-07-21 Jianwei Xu , Lian-He Shao , Shao-Ming Fei

We introduce an elementary measure of non-commutativity between two algebras of quantum operators acting on the same Hilbert space. This quantity, which we call Mutual Averaged Non-commutativity (MAN), is a simple generalization of a type…

Quantum Physics · Physics 2024-06-28 Paolo Zanardi

Quantum coherence is a fundamental characteristic to distinguish quantum systems from their classical counterparts. Though quantum coherence persists in isolated non-interacting systems, interactions inevitably lead to decoherence, which is…

Quantum Gases · Physics 2017-11-15 Ke-Ji Chen , Ho Kwan Lau , Hon Ming Chan , Dajun Wang , Qi Zhou

We address the witnessing of quantum correlations beyond the limits imposed by an ensemble statistical average. By relying upon the continuous observation of a single quantum open system under the action of classical or quantum noise, we…

Quantum Physics · Physics 2016-08-14 Felipe Caycedo-Soler , Ferney J. Rodríguez , Luis Quiroga

The total correlations in a bipartite quantum system are measured by the quantum mutual information $\mathcal{I}$, which consists of quantum discord and classical correlation. However, recent results in quantum information shows that…

Quantum Physics · Physics 2017-10-25 Jin-Xing Hou , Si-Yuan Liu , Xiao-Hui Wang , Wen-Li Yang

We provide a summary of both seminal and recent results on typical entanglement. By typical values of entanglement, we refer here to values of entanglement quantifiers that (given a reasonable measure on the manifold of states) appear with…

Quantum Physics · Physics 2014-09-05 Oscar C. O. Dahlsten , Cosmo Lupo , Stefano Mancini , Alessio Serafini

The coherent information concept is used to analyze a variety of simple quantum systems. Coherent information was calculated for the information decay in a two-level atom in the presence of an external resonant field, for the information…

Quantum Physics · Physics 2009-10-31 B. A. Grishanin , V. N. Zadkov

Quantum coherence as the fundamental characteristic of quantum physics, provides the valuable resource for quantum computation in exceeding the power of classical algorithms. The exploration of quantum coherence in relativistic systems is…

Quantum Physics · Physics 2016-01-13 Xu Chen , Chunfeng Wu , Hong-Yi Su , Chang-Liang Ren , Jing-Ling Chen