近日，东北大学理学院的徐爽及其研究团队取得一项新进展。经过不懈努力，他们确定了纠缠交换中纠缠纯化的形式化界限。相关研究成果已于2025年1月6日在国际知名学术期刊《物理评论A》上发表。

该研究团队研究了基于最优输出态并发度的纠缠交换中的纠缠纯化。首先，对于两个输入纠缠对均处于任意纯态的情况，研究人员给出了描述该过程的严格解析公式。然后，在强有力的数值证据支持下，研究人员将该公式推广到其中一个纠缠对处于任意混合态的情况。

该公式随后给出了纠缠交换中纠缠纯化的形式化上界，以及如何通过设计纯态纠缠对来实现最大纠缠纯化。

此外，上界的形式化还表明，纠缠交换最适合用于减少纯耗散噪声的影响，这可应用于延长量子通信中静止量子比特的寿命。

附：英文原文

Title: Formal bounds of entanglement purification via entanglement swapping

Author: Run-Ze Cong and Shuang Xu*

Issue&Volume: 2025-01-06

Abstract: We study the entanglement purification via entanglement swapping in terms of optimal output state concurrence. A strict formula that governs the process is first given analytically for the case where both input entangled pairs are in arbitrary pure states. Then, it is generalized, with strong numerical evidence, to the case with one of the entangled pairs being in an arbitrary mixed state. The formula subsequently gives a formal upper bound of entanglement purification via entanglement swapping, as well as how the maximum entanglement purification can be attained by engineering the pure state entangled pair. Moreover, the formalism of the upper bound in turn suggests that entanglement swapping is most suited for reducing the influence of pure dissipative noise, which can be applied to extend the lifespan of stationary qubits in quantum communications.

DOI: 10.1103/PhysRevA.111.012409

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.111.012409