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arXiv:1210.0199 · Physical Review B

Experimental protection and revival of quantum correlation in open solid systems

Xing Rong, Fangzhou Jin, Zixiang Wang, Jianpei Geng, Chenyong Ju, Ya Wang, Runmin Zhang, Chang‐Kui Duan, Mingjun Shi, Jiangfeng Du

Published Aug 26, 2013• 25 citations

Abstract

Quantum correlations quantified by quantum discord have been experimentally demonstrated as important physical resources in quantum information processing. Because of the inevitable interactions between the quantum system and the environment, it is essential to characterize the quantum correlation's dynamics in open systems and to protect the quantum correlation from being lost in the environment. Herein it is experimentally demonstrated in the Si:P system that there is a sudden change (at a critical time ${t}_{c}\ensuremath{\approx}166$ ns) in the decay rates of classical and quantum correlations. To protect the quantum correlation, we achieve an extension of the critical time by 50 times to $8\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}$s by applying a two-flip dynamical decoupling pulse sequence. Moreover, we observe the phenomenon of the revival of both quantum and classical correlations. The experimental observation of a nondecay interval for quantum correlation and its great extension in a solid-state system with genuine noise makes the use of quantum discord as a physical resource in quantum information processing more practicable.

DOI: 10.1103/physrevb.88.054419

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Quantum correlations quantified by quantum discord have been experimentally demonstrated as important physical resources in quantum information processing. Because of the inevitable interactions between the quantum system and the environment, it is essential to characterize the quantum correlation's dynamics in open systems and to protect the quantum correlation from being lost in the environment. Herein it is experimentally demonstrated in the Si:P system that there is a sudden change (at a critical time

{t}_{c}\ensuremath{\approx}166

ns) in the decay rates of classical and quantum correlations. To protect the quantum correlation, we achieve an extension of the critical time by 50 times to

8\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}

s by applying a two-flip dynamical decoupling pulse sequence. Moreover, we observe the phenomenon of the revival of both quantum and classical correlations. The experimental observation of a nondecay interval for quantum correlation and its great extension in a solid-state system with genuine noise makes the use of quantum discord as a physical resource in quantum information processing more practicable.

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We study the dynamics of quantum and classical correlations in the presence of nondissipative decoherence. We discover a class of initial states for which the quantum correlations, quantified by the quantum discord, are not destroyed by decoherence for times t<[symbol: see text]. In this initial time interval classical correlations decay. For t>[symbol: see text], on the other hand, classical correlations do not change in time and only quantum correlations are lost due to the interaction with the environment. Therefore, at the transition time [symbol: see text] the open system dynamics exhibits a sudden transition from classical to quantum decoherence regime.

Open quantum systems have attracted great attention, since inevitable coupling between quantum systems and their environment greatly affects the features of interest of these systems. Quantum discord, is a measure of the total nonclassical correlation in a quantum system that includes, but is not exclusive to, the distinct property of quantum entanglement. Quantum discord can exist in separated quantum states and plays an important role in many fundamental physics problems and practical quantum information tasks. There have been numerous investigations on quantum discord and its counterpart classical correlation. This short review focuses on highlighting the system-environment dynamics of two-qubit quantum discord and the influence of initial system-environment correlations on the dynamics of open quantum systems. The external control effect on the dynamics of open quantum systems are involved. Several related experimental works are discussed.

Quantum systems exhibit diversified correlations which have no classical counterparts. It has been pointed out recently that quantum entanglement, the most well known measure of quantum correlations which plays essential roles in quantum information processing, cannot describe all the nonclassicality in the correlations. The quantum discord, which can describe quantum correlations in separable states, is subject to intensive theoretical studies. Herein, we experimentally investigate the quantum correlations of separable thermal states in solids. The sudden changes of the quantum discord are observed, which capture unambiguously the critical points associated with the behavior of the Hamiltonian. Our results display the potential applications of quantum correlations in studying the fundamental properties of quantum systems, such as quantum criticality of nonzero temperatures.

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