scholarly journals Ergotropy from quantum and classical correlations

2021 ◽  
Author(s):  
Akram Touil ◽  
Baris Cakmak ◽  
Sebastian Deffner
Keyword(s):  
Quantum Correlations ◽  
Quantum Systems ◽  
Thermal Bath ◽  
Quantum Properties ◽  
Thermodynamic Work ◽  
Qubit System ◽  
Established Fact ◽  
Quantum Mutual Information ◽  
Quantum And Classical Correlations ◽  
Thermal States

Abstract It is an established fact that quantum coherences have thermodynamic value. The natural question arises, whether other genuine quantum properties such as entanglement can also be exploited to extract thermodynamic work. In the present analysis, we show that the ergotropy can be expressed as a function of the quantum mutual information, which demonstrates the contributions to the extractable work from classical and quantum correlations. More specifically, we analyze bipartite quantum systems with locally thermal states, such that the only contribution to the ergotropy originates in the correlations. Our findings are illustrated for a two-qubit system collectively coupled to a thermal bath.

scholarly journals Generation of Quantum Correlations in Bipartite Gaussian Open Quantum Systems

2018 ◽  
Vol 173 ◽  
pp. 01006 ◽  
Author(s):  
Aurelian Isar
Keyword(s):  
Open Systems ◽  
Thermal Environment ◽  
Open Quantum Systems ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Thermal Bath ◽  
Initial State ◽  
Entanglement Generation ◽  
Strength Of Interaction ◽  
Zero Values

We describe the generation of quantum correlations (entanglement, discord and steering) in a system composed of two coupled non-resonant bosonic modes immersed in a common thermal reservoir, in the framework of the theory of open systems. We show that for separable initial squeezed thermal states entanglement generation may take place, for definite values of squeezing parameter, average photon numbers, temperature of the thermal bath, dissipation constant and strength of interaction between the two bosonic modes. We also show that for initial uni-modal squeezed states Gaussian discord can be generated for all non-zero values of the strength of interaction between the modes. Likewise, for an initial separable state, a generation of Gaussian steering may take place temporarily, for definite values of the parameters characterizing the initial state and the thermal environment, and the strength of coupling between the two modes.

Studying quantum correlations dynamics in the phase space for continuous-variable Werner states and Bell-diagonal states

2019 ◽  
Vol 16 (07) ◽  
pp. 1950109
Author(s):  
Fatima-Zahra Siyouri ◽  
Hicham Ait Mansour ◽  
Fadoua Elbarrichi
Keyword(s):  
Wigner Function ◽  
Quantum Discord ◽  
Open Quantum Systems ◽  
Quantum Correlations ◽  
Continuous Variable ◽  
Quantum Systems ◽  
Qubit System ◽  
Classical Correlations ◽  
Werner States ◽  
System F

We investigate the ability of Wigner function to reveal and measure general quantum correlations in two-qubit open system. For this purpose, we analyze comparatively their dynamics for two different states, continuous-variable Werner states (CWS) and Bell-diagonal states (BDS), independently interacting with dephasing reservoirs. Then, we explore the effects of decreasing the degree of non-Markovianity on their behavior. We show that the presence of both quantum entanglement and quantum discord allow to have a negative Wigner function, in contrast to the result obtained for the closed two-qubit system [F. Siyouri, M. El Baz and Y. Hassouni, The negativity of Wigner function as a measure of quantum correlations, Quantum Inf. Process. 15(10) (2016) 4237–4252]. In fact, we conclude that negativity of Wigner function can be used to capture and quantify the amount of general non-classical correlations in open quantum systems.

DYNAMICAL CONTROL OF QUANTUM CORRELATIONS IN A COMMON ENVIRONMENT

2013 ◽  
Vol 11 (01) ◽  
pp. 1350012 ◽  
Author(s):  
HONGTING SONG ◽  
YU PAN ◽  
ZAIRONG XI
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Common Environment ◽  
Qubit System ◽  
Long Time ◽  
Dynamical Control

Quantum correlations (QC) are generally considered to be the crucial resource for quantum information processing, however, in practice, the inevitable interaction of the quantum systems with the environment can cause decoherence and thus destroy the QC. In this paper, by comparatively studying the model of a two-qubit system in a common environment with and without dynamical control, we show that dynamical control can be exploited to protect QC from being completely destroyed for a long time. For certain product states, the dynamical control can even be used to generate the QC.

GENERALIZED COMPLEMENTARITY RELATIONS IN COMPOSITE QUANTUM SYSTEMS OF ARBITRARY DIMENSIONS

2006 ◽  
Vol 20 (11n13) ◽  
pp. 1371-1381 ◽  
Author(s):  
MATTHIAS JAKOB ◽  
JÁNOS A. BERGOU
Keyword(s):  
Information Content ◽  
Upper Bound ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Quantum Properties ◽  
Wave Particle Duality ◽  
Bipartite Quantum Systems ◽  
Arbitrary Dimensions ◽  
Dependent Factor

Complementarity relations in composite bipartite quantum systems of arbitrary dimensions are proposed. Genuine bipartite quantum properties whose information content is quantified by the generalized concurrence mutually exclude the single-partite properties of the subsystems. The single-partite properties are determined by generalized predictabilities and visibilities, i.e. by the traditional concepts of wave-particle duality and define two complementary realities. These properties combined together are complementary to the generalized I-concurrence which quantifies genuine quantum correlations in n ⊗ m-dimensional bipartite systems. An important feature of the proposed quantitative complementarity relation is its upper bound which is given by a dimensional-dependent factor that exceeds unity in case of qudits with dimensionality d > 2. In d > 2-dimensional systems the information content can exceed one bit of information.

scholarly journals DYNAMICS OF QUANTUM CORRELATIONS IN TWO-QUBIT SYSTEMS WITHIN NON-MARKOVIAN ENVIRONMENTS

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345053 ◽  
Author(s):  
ROSARIO LO FRANCO ◽  
BRUNO BELLOMO ◽  
SABRINA MANISCALCO ◽  
GIUSEPPE COMPAGNO
Keyword(s):  
Quantum Discord ◽  
Open Quantum Systems ◽  
Dynamical Behavior ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Primary Interest ◽  
Common Environment ◽  
Classical Counterpart ◽  
Qubit System ◽  
Dynamics Of Correlations

Knowledge of the dynamical behavior of correlations with no classical counterpart, like entanglement, nonlocal correlations and quantum discord, in open quantum systems is of primary interest because of the possibility to exploit these correlations for quantum information tasks. Here we review some of the most recent results on the dynamics of correlations in bipartite systems embedded in non-Markovian environments that, with their memory effects, influence in a relevant way the system dynamics and appear to be more fundamental than the Markovian ones for practical purposes. Firstly, we review the phenomenon of entanglement revivals in a two-qubit system for both independent environments and a common environment. We then consider the dynamics of quantum discord in non-Markovian dephasing channel and briefly discuss the occurrence of revivals of quantum correlations in classical environments.

HIERARCHY OF CORRELATIONS VIA LÜDERS MEASUREMENTS

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345026 ◽  
Author(s):  
SHUNLONG LUO ◽  
SHUANGSHUANG FU
Keyword(s):  
Quantum Discord ◽  
Schmidt Number ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Quantum States ◽  
Intrinsic Structure ◽  
Fundamental Significance ◽  
Quantum Mutual Information ◽  
Projective Measurements

The classification and quantification of correlations (classical and quantum) in composite quantum systems are of fundamental significance for quantum information processing. While the paradigm of separability versus entanglement has been intensively studied, the scenario of classicality versus quantumness, with focus on the quantum discord, has also attracted many recent interests. In this paper, pursuing further the latter scenario and exploiting the intrinsic structure of bipartite quantum states via local projective measurements, we introduce the notion of coherent dimension of correlations in terms of the Lüders measurements. The coherent dimension can alternatively be regarded as a generalization of the Schmidt number of a pure state. Furthermore, we propose some families of measures for correlations, which extend naturally both the quantum discord and the quantum mutual information (total correlations), and furthermore interpolate between them. These quantities reveal some hierarchial structures, and provide a more complete description, of both classical and quantum correlations in the quantum realm.

scholarly journals A study of quantum correlations in open quantum systems

2011 ◽  
Vol 11 (7&8) ◽  
pp. 541-562
Author(s):  
Indranil Chakrabarty ◽  
Subhashish Banerjee ◽  
Nana Siddharth
Keyword(s):  
Open Quantum Systems ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Bell’S Inequality ◽  
Mixed States ◽  
Classical Correlation ◽  
Bell's Inequality ◽  
Qubit System ◽  
Dynamical Parameters ◽  
Potential Resource

In this work, we study quantum correlations in mixed states. The states studied are modeled by a two-qubit system interacting with its environment via a quantum non demolition (purely dephasing) as well as dissipative type of interaction. The entanglement dynamics of this two qubit system is analyzed. We make a comparative study of various measures of quantum correlations, like Concurrence, Bell's inequality, Discord and Teleportation fidelity, on these states, generated by the above evolutions. We classify these evoluted states on basis of various dynamical parameters like bath squeezing parameter $r$, inter-qubit spacing $r_{12}$, temperature $T$ and time of system-bath evolution $t$. In this study, in addition we report the existence of entangled states which do not violate Bell's inequality, but can still be useful as a potential resource for teleportation. Moreover we study the dynamics of quantum as well as classical correlation in presence of dissipative coherence.

scholarly journals Cyclic quantum causal models

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jonathan Barrett ◽  
Robin Lorenz ◽  
Ognyan Oreshkov
Keyword(s):  
Causal Reasoning ◽  
Causal Structure ◽  
Bell Inequalities ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Causal Models ◽  
Causal Order ◽  
Quantum Processes ◽  
Causal Explanations ◽  
Causal Structures

AbstractCausal reasoning is essential to science, yet quantum theory challenges it. Quantum correlations violating Bell inequalities defy satisfactory causal explanations within the framework of classical causal models. What is more, a theory encompassing quantum systems and gravity is expected to allow causally nonseparable processes featuring operations in indefinite causal order, defying that events be causally ordered at all. The first challenge has been addressed through the recent development of intrinsically quantum causal models, allowing causal explanations of quantum processes – provided they admit a definite causal order, i.e. have an acyclic causal structure. This work addresses causally nonseparable processes and offers a causal perspective on them through extending quantum causal models to cyclic causal structures. Among other applications of the approach, it is shown that all unitarily extendible bipartite processes are causally separable and that for unitary processes, causal nonseparability and cyclicity of their causal structure are equivalent.

scholarly journals Correlations in geometric states

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Wu-zhong Guo
Keyword(s):  
Central Charge ◽  
Convex Combination ◽  
Vacuum State ◽  
Quantum Correlations ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Classical Geometry ◽  
Accessible Information ◽  
Classical Correlations ◽  
Quantum And Classical Correlations

Abstract In this paper we explore the correlations in the geometric states. Here the geometric state means the state in CFTs that can be effectively described by classical geometry in the bulk in the semi-classical limit G → 0. By using the upper bound of Holevo information we show the convex combination of geometric states cannot be a geometric state. To understand the duality between thermofield double state and eternal black hle, we construct several correlated states of two CFTs. In all the examples we show their correlations are too weak to produce the a connected spacetime. Then we review the measure named quantum discord and use it to characterize the classical and quantum correlations in quantum field theories. Finally, we discuss the correlations between two intervals A and B with distance d in the vacuum state of 2D CFTs with large central charge c. The feature is the phase transition of the mutual information I (ρAB). We analyse the quasi-product state of ρAB for large d. By using the Koashi-Winter relation of tripartite states the quantum and classical correlations between A and B can expressed as Holevo information, which provides a new understanding of the correlations as accessible information.

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