Multipartite quantum discord and quantum coherence in Heisenberg–Ising bond alternating chain

Pramana ◽  
2019 ◽  
Vol 93 (6) ◽  
Author(s):  
Wajid Joyia
Keyword(s):  
Quantum Coherence ◽  
Quantum Discord ◽  
Alternating Chain

Nonlocal advantage of quantum coherence under relativistic frame

2018 ◽  
Vol 32 (31) ◽  
pp. 1850377 ◽  
Author(s):  
Long-Fei Wang ◽  
Ming-Ming Du ◽  
Wen-Yang Sun ◽  
Dong Wang ◽  
Liu Ye
Keyword(s):  
Sudden Death ◽  
Quantum Coherence ◽  
Quantum Discord ◽  
Thermal Noise ◽  
Unruh Effect ◽  
Qubit System ◽  
Bell Nonlocality ◽  
Better Than

In this paper, we investigate the influence of the Unruh effect on the achievement of the nonlocal advantage of quantum coherence for a two-qubit system under a relativistic frame. The results show that with the increase of acceleration, it is difficult to realize the nonlocal advantage of quantum coherence and when the acceleration exceeds a certain value, nonlocal advantage of quantum coherence cannot be realized. In addition, we explore the dynamics of Bell nonlocality, steering, quantum coherence, entanglement and quantum discord (QD) under Unruh thermal noise. It is shown that nonlocal advantage of quantum coherence, Bell nonlocality, steering and entanglement experience “sudden death” for a finite acceleration, while quantum coherence and QD vanish only in the limit of an infinite acceleration. We also find that not all nonlocal states can achieve the nonlocal advantage of quantum coherence. It is also demonstrated that the robustness of Bell nonlocality is better than nonlocal advantage of quantum coherence under the influence of the Unruh noise.

scholarly journals Quantum coherence versus nonclassical correlations in optomechanics

2019 ◽  
Vol 33 (29) ◽  
pp. 1950343
Author(s):  
Y. Lahlou ◽  
M. Amazioug ◽  
J. El Qars ◽  
N. Habiballah ◽  
M. Daoud ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Quantum Coherence ◽  
Quantum Discord ◽  
Thermal Noise ◽  
Superposition Principle ◽  
Quantum Correlations ◽  
Entanglement Of Formation ◽  
Mechanical Subsystem ◽  
Optomechanical Coupling ◽  
Gaussian Quantum Discord

Coherence arises from the superposition principle, where it plays a central role in quantum mechanics. In Phys. Rev. Lett. 114, 210401 (2015), it has been shown that the freezing phenomenon of quantum correlations beyond entanglement is intimately related to the freezing of quantum coherence (QC). In this paper, we compare the behavior of entanglement and quantum discord with quantum coherence in two different subsystems (optical and mechanical). We use respectively the entanglement of formation (EoF) and the Gaussian quantum discord (GQD) to quantify entanglement and quantum discord. Under thermal noise and optomechanical coupling effects, we show that EoF, GQD and QC behave in the same way. Remarkably, when entanglement vanishes, GQD and QC remain almost unaffected by thermal noise, keeping nonzero values even for high-temperature, which is in concordance with Phys. Rev. Lett. 114, 210401 (2015). Also, we find that the coherence associated with the optical subsystem is more robust — against thermal noise — than those of the mechanical subsystem. Our results confirm that optomechanical cavities constitute a powerful resource of QC.

Dynamics of coherence under Markovian and non-Markovian environments

2017 ◽  
Vol 31 (35) ◽  
pp. 1750329 ◽  
Author(s):  
Zhong-Xiao Wang ◽  
Teng Ma ◽  
Shu-Hao Wang ◽  
Tie-Jun Wang ◽  
Chuan Wang
Keyword(s):  
Density Matrix ◽  
Upper Bound ◽  
Quantum Coherence ◽  
Quantum Discord ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Initial State ◽  
Single Qubit ◽  
Markovian Processes ◽  
Markovian Dynamics

The behavior of quantum coherence is studied under Markovian and non-Markovian dynamics for open quantum systems. For single qubit systems, we show that the coherence depending on the off-diagonal elements of the density matrix is the upper bound of the coherence depending on the relative entropy under both Markovian and non-Markovian processes. For two-qubit systems, in both Markovian and non-Markovian processes, quantum discord and coherence show less sensitivity to the initial state than quantum entanglement. We also find that the quantum discord has similar behaviors with coherence under both Markovian and non-Markovian dynamics.

scholarly journals QUANTUM DISCORD AS A RESOURCE IN QUANTUM COMMUNICATION

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345041 ◽  
Author(s):  
VAIBHAV MADHOK ◽  
ANIMESH DATTA
Keyword(s):  
Quantum State ◽  
Quantum Coherence ◽  
Quantum Discord ◽  
Quantum Communication ◽  
Quantum States ◽  
Quantitative Relation ◽  
Dense Coding ◽  
Open Questions ◽  
Communication Processes ◽  
Quantum Protocols

As quantum technologies move from the issues of principle to those of practice, it is important to understand the limitations on attaining tangible quantum advantages. In the realm of quantum communication, quantum discord captures the damaging effects of a decoherent environment. This is a consequence of quantum discord quantifying the advantage of quantum coherence in quantum communication. This establishes quantum discord as a resource for quantum communication processes. We discuss this progress, which derives a quantitative relation between the yield of the fully quantum Slepian–Wolf (FQSW) protocol in the presence of noise and the quantum discord of the state involved. The significance of quantum discord in noisy versions of teleportation, super-dense coding, entanglement distillation and quantum state merging are discussed. These results lead to open questions regarding the tradeoff between quantum entanglement and discord in choosing the optimal quantum states for attaining palpable quantum advantages in noisy quantum protocols.

scholarly journals Quantum coherence and geometric quantum discord

2018 ◽  
Vol 762-764 ◽  
pp. 1-100 ◽  
Author(s):  
Ming-Liang Hu ◽  
Xueyuan Hu ◽  
Jieci Wang ◽  
Yi Peng ◽  
Yu-Ran Zhang ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Quantum Discord ◽  
Geometric Quantum Discord

Engineering Electronic Structure to Protect Phase Memory in Molecular Qubits by Minimising Orbital Angular Momentum

2018 ◽  
Author(s):  
Ana Maria Ariciu ◽  
David H. Woen ◽  
Daniel N. Huh ◽  
Lydia Nodaraki ◽  
Andreas Kostopoulos ◽  
...  
Keyword(s):  
Electron Spin ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Pulse Sequences ◽  
Grover Algorithm ◽  
Ligand Shell ◽  
Information Strategies ◽  
Spin Qubit ◽  
Molecular Spin ◽  
The Impact

Using electron spins within molecules for quantum information processing (QIP) was first proposed by Leuenberger and Loss (1), who showed how the Grover algorithm could be mapped onto a Mn12 cage (2). Since then several groups have examined two-level (S = ½) molecular spin systems as possible qubits (3-12). There has also been a report of the implementation of the Grover algorithm in a four-level molecular qudit (13). A major challenge is to protect the spin qubit from noise that causes loss of phase information; strategies to minimize the impact of noise on qubits can be categorized as corrective, reductive, or protective. Corrective approaches allow noise and correct for its impact on the qubit using advanced microwave pulse sequences (3). Reductive approaches reduce the noise by minimising the number of nearby nuclear spins (7-11), and increasing the rigidity of molecules to minimise the effect of vibrations (which can cause a fluctuating magnetic field via spin-orbit coupling) (9,11); this is essentially engineering the ligand shell surrounding the electron spin. A protective approach would seek to make the qubit less sensitive to noise: an example of the protective approach is the use of clock transitions to render spin states immune to magnetic fields at first order (12). Here we present a further protective method that would complement reductive and corrective approaches to enhancing quantum coherence in molecular qubits. The target is a molecular spin qubit with an effective 2S ground state: we achieve this with a family of divalent rare-earth molecules that have negligible magnetic anisotropy such that the isotropic nature of the electron spin renders the qubit markedly less sensitive to magnetic noise, allowing coherent spin manipulations even at room temperature. If combined with the other strategies, we believe this could lead to molecular qubits with substantial advantages over competing qubit proposals.<br>

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