BIPARTITE AND MULTIPARTITE CORRELATIONS OF COUPLED QUBITS IN A NON-MARKOVIAN ENVIRONMENT: HIERARCHY EQUATION METHOD

2013 ◽  
Vol 11 (06) ◽  
pp. 1350058 ◽  
Author(s):  
JIAN-SONG ZHANG ◽  
ZHI-YUAN HUANG ◽  
AI-XI CHEN
Keyword(s):  
Quantum Information ◽  
Sudden Death ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Spin Squeezing ◽  
Equation Method ◽  
Entanglement Sudden Death ◽  
Markovian Approximations ◽  
Rotating Wave ◽  
Coupled Qubits

We study bipartite and multipartite correlations of several coupled qubits within a common non-Markovian bath using the hierarchy equation method. This method does not use the rotating-wave and Born–Markovian approximations. The interaction between the qubits and their coupling strength with the bath have remarkable influence on the dynamics of quantum correlations. The entanglement sudden death (ESD) phenomenon, the amount of stationary state concurrence and spin squeezing can be controled by the non-Markovianity of the environment and interactions between qubits. These properties may be useful for purposes of quantum information processing with multiqubit system in non-Markovian environments.

Thermal geometric discords in a two-qutrit system

2016 ◽  
Vol 14 (03) ◽  
pp. 1650016 ◽  
Author(s):  
Ya-Li Yuan ◽  
Xi-Wen Hou
Keyword(s):  
Magnetic Field ◽  
Quantum Information ◽  
Magnetic Fields ◽  
Weak Magnetic Field ◽  
Quantum Discord ◽  
Quantum Information Processing ◽  
Thermal State ◽  
Quantum Correlations ◽  
High Dimensional ◽  
Lower Temperature

The investigation of quantum discord has mostly focused on two-qubit systems due to the complicated minimization involved in quantum discord for high-dimensional states. In this work, three geometric discords are studied for the thermal state in a two-qutrit system with various couplings, external magnetic fields, and temperatures as well, where the entanglement measured in terms of the generalized negativity is calculated for reference. It is shown that three geometric discords are more robust against temperature and magnetic field than the entanglement negativity. However, all four quantities exhibit a similar behavior at lower temperature and weak magnetic field. Remarkably, three geometric discords at finite temperature reveal the phenomenon of double sudden changes at different magnetic fields while the negativity does not. Moreover, the hierarchy among three discords is discussed. Those adjustable discords with the varied coupling, temperature, and magnetic field are useful for the understanding of quantum correlations in high-dimensional states and quantum information processing.

scholarly journals Local available quantum correlations for Bell Diagonal states and Markovian decoherence

2018 ◽  
Vol 64 (6) ◽  
pp. 662
Author(s):  
Hermann L Albrecht Q ◽  
Douglas F. Mundarain ◽  
Mario I. Caicedo S.
Keyword(s):  
Sudden Death ◽  
Quantum Discord ◽  
Quantum Correlations ◽  
Entanglement Sudden Death ◽  
Dissipative Dynamics ◽  
Phase Damping ◽  
Werner States ◽  
Kraus Operators

Local available quantum correlations (LAQCs), as dened by Mundarain et al. [19], are analytically determined for Bell Diagonal states. Using the Kraus operators formalism [10], we analyze the dissipative dynamics of 2-qubit LAQCs under Markovian decoherence. This is done for Werner states under the depolarizing [20] and phase damping channels [21]. Since Werner states are among those that exhibit the so called entanglement sudden death [27], the results are compared with the ones obtained for Quantum Discord [22], as analyzed by Werlang et al. [24], as well as for entanglement, i.e. Concurrence[7]. The LAQCs quantier, as Quantum Discord does, only vanishes asymptotically.

scholarly journals Remote State Design for Efficient Quantum Metrology with Separable and Non-Teleporting States

2021 ◽  
Vol 3 (1) ◽  
pp. 228-241
Author(s):  
Rahul Raj ◽  
Shreya Banerjee ◽  
Prasanta K. Panigrahi
Keyword(s):  
Parameter Estimation ◽  
Quantum Information ◽  
Fisher Information ◽  
Quantum Information Processing ◽  
Quantum Fisher Information ◽  
Quantum Correlations ◽  
Quantum States ◽  
Quantum Metrology ◽  
High Quantum ◽  
Non Local

Measurements leading to the collapse of states and the non-local quantum correlations are the key to all applications of quantum mechanics as well as in the studies of quantum foundation. The former is crucial for quantum parameter estimation, which is greatly affected by the physical environment and the measurement scheme itself. Its quantification is necessary to find efficient measurement schemes and circumvent the non-desirable environmental effects. This has led to the intense investigation of quantum metrology, extending the Cramér–Rao bound to the quantum domain through quantum Fisher information. Among all quantum states, the separable ones have the least quantumness; being devoid of the fragile non-local correlations, the component states remain unaffected in local operations performed by any of the parties. Therefore, using these states for the remote design of quantum states with high quantum Fisher information can have diverse applications in quantum information processing; accurate parameter estimation being a prominent example, as the quantum information extraction solely depends on it. Here, we demonstrate that these separable states with the least quantumness can be made extremely useful in parameter estimation tasks, and further show even in the case of the shared channel inflicted with the amplitude damping noise and phase flip noise, there is a gain in Quantum Fisher information (QFI). We subsequently pointed out that the symmetric W states, incapable of perfectly teleporting an unknown quantum state, are highly effective for remotely designing quantum states with high quantum Fisher information.

The dynamics of tripartite quantum correlations under Ornstein–Uhlenbeck noise

2018 ◽  
Vol 32 (31) ◽  
pp. 1850381 ◽  
Author(s):  
Jing Yang ◽  
Qi-Xiong Mu ◽  
Yan-Xia Huang
Keyword(s):  
Magnetic Field ◽  
Sudden Death ◽  
Quantum Correlation ◽  
Quantum Correlations ◽  
Time Limit ◽  
Entanglement Sudden Death ◽  
Thermal Entanglement ◽  
Short Time ◽  
The Magnetic Field ◽  
Markov Limit

The dynamics of the tripartite thermal entanglement measured by Negativity (N) and the tripartite quantum correlation described by measurement-induced disturbance (MID) under Ornstein–Uhlenbeck noise are investigated. This study has found that the tripartite N and MID can be preserved more effectively in the non-Markovian environment than in the short-time limit and the Markov limit cases. The short-time limit is a better approximation than the Markov limit. MID vanishes only in the asymptotic limit, while entanglement sudden death may occur, and the decreasing duration of MID far outweighs entanglement. This implies that MID is more robust than Negativity. As the noise bandwidth increases, the disentanglement time and the decay time of MID are significantly shorter. The increase of XZX[Formula: see text]+[Formula: see text]YZY three-site interaction is more effective than XZY−YZX three-site interaction to enhance Negativity and MID as well as the disentanglement time. The magnetic field diminishes Negativity and MID, but has no significant influence on the decreasing durations of both Negativity and MID.

scholarly journals Solid-state multiple quantum NMR in quantum information processing: exactly solvable models

2012 ◽  
Vol 370 (1976) ◽  
pp. 4690-4712 ◽  
Author(s):  
E. B. Fel'dman ◽  
A. N. Pyrkov ◽  
A. I. Zenchuk
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Solid State ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Multiple Quantum ◽  
Exactly Solvable Models ◽  
Solvable Models ◽  
Exactly Solvable ◽  
Large Clusters

Multiple quantum (MQ) NMR is an effective tool for the generation of a large cluster of correlated particles, which, in turn, represent a basis for quantum information processing devices. Studying the available exactly solvable models clarifies many aspects of the quantum information. In this study, we consider two exactly solvable models in the MQ NMR experiment: (i) the isolated system of two spin- particles (dimers) and (ii) the large system of equivalent spin- particles in a nanopore. The former model is used to describe the quantum correlations and their relations with the MQ NMR coherences, whereas the latter helps one to model the creation and decay of large clusters of correlated particles.

QUANTUM CORRELATIONS OF TWO SPIN-1 PARTICLES IN THE OPTICAL LATTICE

2014 ◽  
Vol 28 (10) ◽  
pp. 1450049 ◽  
Author(s):  
JIA-DONG SHI ◽  
TAO WU ◽  
XUE-KE SONG ◽  
LIU YE
Keyword(s):  
Phase Transition ◽  
Sudden Death ◽  
Critical Point ◽  
Quantum Phase Transition ◽  
Finite Temperature ◽  
Optical Lattice ◽  
Quantum Correlations ◽  
Entanglement Sudden Death ◽  
Superfluid Phase ◽  
Dynamical Behaviors

In this paper, we investigate the dynamical behaviors of quantum correlations witnessed by geometric discord and negativity when two three-level spin-1 atoms exist in the optical lattice. The results show that the GD can detect the critical point K = J at finite temperature associated with the quantum phase transition which separates the superfluid phase from the Mott insulator phase, while the negativity cannot. In addition, the system undergoes an entanglement sudden death (ESD), but the GD always exists, meanwhile, the GD is more robust than negativity against temperature T.

scholarly journals Quantum Bounds on Detector Efficiencies for Violating Bell Inequalities Using Semidefinite Programming

Cryptography ◽  
2020 ◽  
Vol 4 (1) ◽  
pp. 2
Author(s):  
Alexander Sauer ◽  
Gernot Alber
Keyword(s):  
Quantum Information ◽  
Quantum Key Distribution ◽  
Quantum Information Processing ◽  
Bell Inequalities ◽  
Quantum Correlations ◽  
Quantum Nonlocality ◽  
Semidefinite Programs ◽  
Dark Counts ◽  
Optimal Inequality ◽  
Detector Model

Loophole-free violations of Bell inequalities are crucial for fundamental tests of quantum nonlocality. They are also important for future applications in quantum information processing, such as device-independent quantum key distribution. Based on a detector model which includes detector inefficiencies and dark counts, we estimate the minimal requirements on detectors needed for performing loophole-free bipartite and tripartite Bell tests. Our numerical investigation is based on a hierarchy of semidefinite programs for characterizing possible quantum correlations. We find that for bipartite setups with two measurement choices and our detector model, the optimal inequality for a Bell test is equivalent to the Clauser–Horne inequality.

Measurement-induced nonlocality in the two-qubit Heisenberg XY model

2015 ◽  
Vol 29 (15) ◽  
pp. 1550098 ◽  
Author(s):  
Wen-Xue Chen ◽  
Yu-Xia Xie ◽  
Xiao-Qiang Xi
Keyword(s):  
Magnetic Field ◽  
Information Processing ◽  
Quantum Information ◽  
External Magnetic Field ◽  
Potential Application ◽  
Quantum Correlation ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Xy Model ◽  
Anisotropic Parameter

Quantum correlations are essential for quantum information processing (QIP). Measurement-induced nonlocality (MIN) is a good measure of quantum correlation, and is favored for its conceptual implication and potential application. We investigated here the particular behaviors of the geometric and entropic measures of MIN in the two-qubit Heisenberg XY model and revealed the effects of anisotropic parameter γ and the external magnetic field B on them. Our results showed that both γ and B can serve as efficient controlling parameters for tuning MIN in the XY model.

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