Violation of Clauser–Horne–Shimony–Holt inequality and teleportation enhanced for a class of two-qubit X-states resulting from entanglement swapping

Li, Shu-Cheng; Song, Wei; Yang, Ming; Zhang, Gang; Cao, Zhuo‐Liang

doi:10.1007/s11128-015-1077-y

Cited by 4 publications

(1 citation statement)

References 17 publications

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“…The entanglement swapping, as a mechanism for distributing the entanglement correlation, has been extensively studied both theoretically and experimentally [10,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Threshold effect for probabilistic entanglement swapping

Roa¹,

Purz²,

Muñoz³

et al. 2021

Preprint

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The basic entanglement swapping protocol allows to achieve the main aim of deterministically projecting two qubits, which have never interacted, onto a maximally entangled state. For deterministic swapping the key ingredient is the maximal entanglement initially contained in two pairs of qubits and the ability to measure onto a Bell basis. In other words, the basic and deterministic entanglement swapping scheme involves three maximal level of entanglement. In this work we address probabilistic entanglement swapping processes performed with different amounts of initial entanglement. Besides, we suggest a non Bell measuring-basis, thus we introduce a third entanglement level in the process. Additionally, we propose the unambiguous state extraction scheme as the local mechanism for probabilistically achieving the main aim. Amalgamating these three elements allows us to design four strategies for performing probabilistic entanglement swapping. Surprisingly, we encountered an twofold entanglement matching effect related to the concurrence of the measuring-basis. Specifically, the maximal probability of accomplishing the main aim becomes a constant for concurrences higher than or equal to the matching entanglement values. Thus, we show that maximal entanglement in the measuring-basis is not required for attaining the main aim with optimal probability.

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Section: Introductionmentioning

confidence: 99%

Threshold effect for probabilistic entanglement swapping

Roa¹,

Purz²,

Muñoz³

et al. 2021

Preprint

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Activating the Violation of Steering Inequality for Two‐Qubit X States

et al. 2019

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The phenomenon of superactivation of quantum steering, that is, the fact that by combining several copies of the unsteerable quantum state one can get a steerable quantum state, has recently attracted much attention. This property is currently only known for isotropic states, and whether there exists an example other than isotropic states is so far an open question. It is of great importance to learn the activation property of non-isotropic states. In this paper, it is shown that the violation of the local uncertainty relations (LUR) steering inequality can be activated for two-qubit X type entangled mixed states. Although the activation phenomenon proven in this paper cannot guarantee the superactivation of steering for two-qubit X states, it does provide clues for this goal. In addition, previous results indicate that two copies are enough for the superactivation of steering, while the price to pay is a high local dimension, and it is unclear whether superactivation is possible with few copies in low-dimensional systems such as two-qubit systems. By providing examples of activation of LUR steering inequality with two copies in a two-qubit system, the work may open a potential way to the solution of this question.

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