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Gaussian quantum discord is a measure of quantum correlations in Gaussian systems. Using Gaussian discord we quantify the quantum correlations of a bipartite entangled state and a separable two-mode mixture of coherent states. We…

Quantum Physics · Physics 2012-08-13 Lars S. Madsen , Adriano Berni , Mikael Lassen , Ulrik L. Andersen

We compare entanglement with quantum nonlocality employing a geometric structure of the state space of bipartite qudits. Central object is a regular simplex spanned by generalized Bell states. The Collins-Gisin-Linden-Massar-Popescu-Bell…

Quantum Physics · Physics 2015-03-13 Christoph Spengler , Marcus Huber , Beatrix C. Hiesmayr

In an idealistic setting, quantum metrology protocols allow to sense physical parameters with mean squared error that scales as $1/N^2$ with the number of particles involved---substantially surpassing the $1/N$-scaling characteristic to…

Quantum Physics · Physics 2015-01-05 Jan Kolodynski

One of the best signatures of nonclassicality in a quantum system is the existence of correlations that have no classical counterpart. Different methods for quantifying the quantum and classical parts of correlations are amongst the more…

Quantum Physics · Physics 2012-11-29 Kavan Modi , Aharon Brodutch , Hugo Cable , Tomasz Paterek , Vlatko Vedral

It is well known that correlations predicted by quantum mechanics cannot be explained by any classical (local-realistic) theory. The relative strength of quantum and classical correlations is usually studied in the context of Bell…

Quantum mechanics can produce correlations that are stronger than classically allowed. This stronger-than-classical correlation is the "fuel" for quantum computing. In 1991 Schumacher forwarded a beautiful geometric approach, analogous to…

We introduce a geometric quantification of quantum coherence in single-mode Gaussian states and we investigate the behavior of distance measures as functions of different physical parameters. In the case of squeezed thermal states, we…

We exhibit three inequalities involving quantum measurement, all of which are sharp and state independent. The first inequality bounds the performance of joint measurement. The second quantifies the trade-off between the measurement quality…

Quantum Physics · Physics 2021-08-18 Bas Janssens

From an operational perspective, quantumness characterizes the exotic behavior in a physical process which cannot be explained with Newtonian physics. There are several widely used measures of quantumness, including coherence, discord, and…

Quantum Physics · Physics 2018-01-31 Xiao Yuan , Hongyi Zhou , Mile Gu , Xiongfeng Ma

We study the relative strength of classical and quantum correlations, as measured by discord, for two-qubit states. Quantum correlations appear only in the presence of classical correlations, while the reverse is not always true. We…

Quantum Physics · Physics 2011-01-17 Fernando Galve , Gian Luca Giorgi , Roberta Zambrini

We address the experimental estimation of Gaussian quantum discord for two-mode squeezed thermal state, and demonstrate a measurement scheme based on a pair of homodyne detectors assisted by Bayesian analysis which provides nearly optimal…

For any bipartite state, how strongly can one subsystem be quantum correlated with another? Using the Koashi-Winter relation, we study the upper bound of purified quantum discord, which is given by the sum of the von Neumann entropy of the…

Quantum Physics · Physics 2014-11-17 Feng Liu , Guo-Jing Tian , Su-Juan Qin , Qiao-Yan Wen , Fei Gao

Quantum discord is usually referred to as a measure for quantum correlations. In the search of the fundamental resource to gain a quantum advantage in quantum information applications, quantum discord is considered a promising candidate. In…

Quantum Physics · Physics 2012-06-04 Manuel Gessner , Elsi-Mari Laine , Heinz-Peter Breuer , Jyrki Piilo

We show that only those composite quantum systems possessing nonvanishing quantum correlations have the property that any nontrivial local unitary evolution changes their global state. We derive the exact relation between the global state…

Quantum Physics · Physics 2013-01-17 S. M. Giampaolo , A. Streltsov , W. Roga , D. Bruß , F. Illuminati

In this paper, we argue that quantum coherence in a bipartite system can be contained either locally or in the correlations between the subsystems. The portion of quantum coherence contained within correlations can be viewed as a kind…

Quantum Physics · Physics 2016-08-31 Kok Chuan Tan , Hyukjoon Kwon , Chae-Yeun Park , Hyunseok Jeong

We show that trace distance measure of coherence is a strong monotone for all qubit and, so called, $X$ states. An expression for the trace distance coherence for all pure states and a semi definite program for arbitrary states is provided.…

Quantum Physics · Physics 2016-01-22 Swapan Rana , Preeti Parashar , Maciej Lewenstein

The quantum corrections to black hole entropy, variously defined, suffer quadratic divergences reminiscent of the ones found in the renormalization of the gravitational coupling constant (Newton constant). We consider the suggestion, due to…

High Energy Physics - Theory · Physics 2009-10-28 Finn Larsen , Frank Wilczek

Quantum correlations represent a fundamental tool for studies ranging from basic science to quantum technologies. Different non-classical correlations have been identified and studied, as entanglement and discord. In view of future…

Quantum Physics · Physics 2016-12-15 E. Moreva , M. Gramegna , M. A. Yurischev , M. Genovese

Many of the standard Bell inequalities (e.g., CHSH) are not effective for detection of quantum correlations which allow for steering, because for a wide range of such correlations they are not violated. We present Bell-like inequalities…

Quantum Physics · Physics 2015-04-14 Marek Żukowski , Arijit Dutta , Zhi Yin

Quantum discord is an important measure of quantum correlations that can serve as a resource for certain types of quantum information processing. \ Like entanglement, discord is subject to destruction by external noise. The routes by which…

Quantum Physics · Physics 2013-10-22 Nga T. T. Nguyen , Robert Joynt
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