Thermal quantum correlations in a two-qubit Heisenberg XYZ model with different magnetic fields

2015 ◽  
Vol 13 (06) ◽  
pp. 1550046 ◽  
Author(s):  
Zheng Hu ◽  
Yu-Chen Wang ◽  
Xi-Wen Hou
Keyword(s):  
Magnetic Field ◽  
Information Processing ◽  
Quantum Information ◽  
Magnetic Fields ◽  
Finite Temperature ◽  
Quantum Discord ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Field Coupling ◽  
Magnetic Field Coupling

Two kinds of thermal quantum correlations, measured respectively by quantum discord (QD) and the generalized negativity (GN), are studied for various magnetic fields, couplings, and temperatures in a two-qubit Heisenberg XYZ model. It is shown that QD and GN can exhibit a similar behavior in some regions of magnetic field, coupling, and temperature, while they behave in a contrary manner in other regions. For example, QD may increase with suitable magnetic fields, couplings, and temperature when GN decreases. QD is more robust against temperature than GN, and can reveal a kink at a suitable coupling at finite temperature while GN cannot. Moreover, a nearly unchanged QD or GN can be obtained in a large region of magnetic field, coupling, and temperature. These adjustable QD and GN via the varied magnetic field, coupling, and temperature may have significant applications in quantum information processing.

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.

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.

scholarly journals Dynamics of entanglement and non-classical correlation for four-qubit GHZ state

2015 ◽  
Vol 13 (06) ◽  
pp. 1550044 ◽  
Author(s):  
P. Espoukeh ◽  
R. Rahimi ◽  
S. Salimi ◽  
P. Pedram
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Discord ◽  
Quantum Information Processing ◽  
Ghz State ◽  
Classical Correlation ◽  
Qubit System ◽  
The Many ◽  
Sudden Transition

Many-qubit entanglement is crucial for quantum information processing although its exploitation is hindered by the detrimental effects of the environment surrounding the many-qubit system. It is thus of importance to study the dynamics of general multipartite non-classical correlation, including but not restricted to entanglement, under noise. We did this study for four-qubit Greenberger–Horne–Zeilinga (GHZ) state under most common noises in an experiment and found that non-classical correlation is more robust than entanglement except when it is imposed to dephasing channel. Quantum discord presents a sudden transition in its dynamics for Pauli-X and Pauli-Y noises as well as Bell-diagonal states interacting with dephasing reservoirs and it decays monotonically for Pauli-Z and isotropic noises.

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.

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.

scholarly journals Quantum information processing by nuclear magnetic resonance on quadrupolar nuclei

2012 ◽  
Vol 370 (1976) ◽  
pp. 4770-4793 ◽  
Author(s):  
João Teles ◽  
Eduardo R. DeAzevedo ◽  
Jair C. C. Freitas ◽  
Roberto S. Sarthour ◽  
Ivan S. Oliveira ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Information Processing ◽  
Quantum Information ◽  
Magnetic Resonance ◽  
Quantum Information Processing ◽  
Quantum Correlations ◽  
Quadrupolar Nuclei ◽  
Quadrupole Resonance ◽  
State Tomography ◽  
Nuclear Magnetic

Nuclear magnetic resonance is viewed as an important technique for the implementation of many quantum information algorithms and protocols. Although the most straightforward approach is to use the two-level system composed of spin nuclei as qubits, quadrupolar nuclei, which possess a spin greater than , are being used as an alternative. In this study, we show some unique features of quadrupolar systems for quantum information processing, with an emphasis on the ability to execute efficient quantum state tomography (QST) using only global rotations of the spin system, whose performance is shown in detail. By preparing suitable states and implementing logical operations by numerically optimized pulses together with the QST method, we follow the stepwise execution of Grover's algorithm. We also review some work in the literature concerning the relaxation of pseudo-pure states in spin systems as well as its modelling in both the Redfield and Kraus formalisms. These data are used to discuss differences in the behaviour of the quantum correlations observed for two-qubit systems implemented by spin and quadrupolar spin systems, also presented in the literature. The possibilities and advantages of using nuclear quadrupole resonance experiments for quantum information processing are also discussed.

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