Coherence-controlled entanglement and nonlocality of two qubits interacting with a thermal reservoir

Liao, Xiang-Ping; Mao-Fa, Fang; Zheng, Xuejun; Jian-Wu, Cai

doi:10.1016/j.physleta.2007.03.039

Cited by 16 publications

(18 citation statements)

References 28 publications

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“…It is worth mentioning that the dynamics of entanglement when initial state is the Bell state had been studied in Ref. [42]. Now, we obtain the same result about the quantum discord as the former investigation about the quantum entanglement when initial state is the Bell state.…”

Section: The Dynamics Of Discord and Entanglement Between Two Qubitssupporting

confidence: 79%

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Steady-State Discord Between Two Qubits Coupled Collectively to a Thermal Reservoir

et al. 2011

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We study the dynamics of quantum discord between two qubits coupled collectively to a thermal reservoir. For comparison, we also consider the dynamics of quantum entanglement. It is shown that we can obtain a stable quantum discord induced by the thermal environment when the discord of the initial state is zero. The thermal environment can also induce a stable amplification of the initially prepared quantum discord for certain Xtype states. It is very valuable that the quantum discord is more resistant against the thermal environment than quantum entanglement. And, we have demonstrated that the sudden death of discord in a Markovian regime is impossible even at high temperature. It provides us a feasible way to create and protect quantum correlation in the case of a high-temperature thermal environment for various physical system such as trapped ions, quantum dots or Josephson junctions.

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Section: The Dynamics Of Discord and Entanglement Between Two Qubitssupporting

confidence: 79%

“…Under the Markovian approximation, the dynamical behavior of two qubits in this case can be described by the following master equation [41,42] …”

Section: The Master Equation and The Solutionmentioning

confidence: 99%

Steady-State Discord Between Two Qubits Coupled Collectively to a Thermal Reservoir

et al. 2011

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“…Note that many other comparative studies of the concurrence and CHSH violation were limited to some specific classes of two-qubit states usually in a dynamical context [18][19][20][21][22][23][24][25][26].…”

Section: Arxiv:13066504v2 [Quant-ph] 19 Nov 2013mentioning

confidence: 99%

Entanglement estimation from Bell inequality violation

et al. 2013

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It is well known that the violation of Bell's inequality in the form given by Clauser, Horne, Shimony, and Holt (CHSH) in two-qubit systems requires entanglement, but not vice versa, i.e., there are entangled states which do not violate the CHSH inequality. Here we compare some standard entanglement measures with violations of the CHSH inequality (as given by the Horodecki measure) for two-qubit states generated by Monte Carlo simulations. We describe states that have extremal entanglement according to the negativity, concurrence, and relative entropy of entanglement for a given value of the CHSH violation. We explicitly find these extremal states by applying the generalized method of Lagrange multipliers based on the Karush-Kuhn-Tucker conditions. The found minimal and maximal states define the range of entanglement accessible for any two-qubit states that violate the CHSH inequality by the same amount. We also find extremal states for the concurrence versus negativity by considering only such states which do not violate the CHSH inequality. Furthermore, we describe an experimentally efficient linear-optical method to determine the highest Horodecki degree of the CHSH violation for arbitrary mixed states of two polarization qubits. By assuming to have access simultaneously to two copies of the states, our method requires only six discrete measurement settings instead of nine settings, which are usually considered.

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“…In Ref. [27], the author has studied the entanglement and the nonlocality of two qubits interacting with a thermal reservoir. The results show that the common thermal resevoir can enhance the entanglement of two qubits when two qubits are initially in coherent states.…”

Section: Introductionmentioning

confidence: 99%

Coherence-controlled stationary entanglement between two atoms embedded in a bad cavity injected with squeezed vacuum

2014

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Abstract:We investigate the entanglement between two atoms in an overdamped cavity injected with squeezed vacuum when these two atoms are initially prepared in coherent states. It is shown that the stationary entanglement exhibits a strong dependence on the initial state of the two atoms when the spontaneous emission rate of each atom is equal to the collective spontaneous emission rate, corresponding to the case where the two atoms are close together. It is found that the stationary entanglement of two atoms increases with decreasing effective atomic cooperativity parameter. The squeezed vacuum can enhance the entanglement of two atoms when the atoms are initially in coherent states. Valuably, this provides us with a feasible way to manipulate and control the entanglement, by changing the relative phases and the amplitudes of the polarized atoms and by varying the effective atomic cooperativity parameter of the system, even though the cavity is a bad one. When the spontaneous emission rate of each atom is not equal to the collective spontaneous emission rate, the steady-state entanglement of two atoms always maintains the same value, as the amplitudes of the polarized atoms varies. Moreover, the larger the degree of two-photon correlation, the stronger the steady-state entanglement between the atoms. PACS

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Coherence-controlled entanglement and nonlocality of two qubits interacting with a thermal reservoir

Cited by 16 publications

References 28 publications

Steady-State Discord Between Two Qubits Coupled Collectively to a Thermal Reservoir

Steady-State Discord Between Two Qubits Coupled Collectively to a Thermal Reservoir

Entanglement estimation from Bell inequality violation

Coherence-controlled stationary entanglement between two atoms embedded in a bad cavity injected with squeezed vacuum

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