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arXiv 2111.04420quant-phphysics.optics
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光致纠缠恢复

Propagation-induced entanglement revival

Abhinandan Bhattacharjee, Mritunjay K. Joshi, Suman Karan, Jonathan Leach, Anand K. Jha

摘要:

自由空间量子信息任务的实际实现需要在长距离和湍流和噪声环境中保持纠缠。参量下转换产生的光子对的横向位置-动量纠缠在量子信息科学中有着广泛的应用,但当光子远离源传播时,纠缠会迅速衰减,不适合长距离传输的应用。纠缠在传播几厘米后就消失了,这种效果在湍流环境中变得更加明显。相比之下,在这篇文章中,我们表明,纠缠在角轨道角动量(OAM)基地表现出显着不同的行为。与位置-动量的情况一样,最初,角-OAM纠缠随着传播而衰减,但随着光子继续远离源,光子恢复其强相关行为,纠缠恢复。我们从理论和实验上证明了这种行为,并表明,纠缠返回,即使在强湍流的存在。湍流的唯一作用是增加复活的传播距离,但是一旦复活,两个光子在任意传播距离上保持纠缠。这项工作突出了OAM角纠缠将在长距离共享量子信息的应用中发挥的作用。

英文摘要:

The practical implementation of free-space quantum information tasks requires entanglement to be sustained over long distances and in the presence of turbulent and noisy environments. The transverse position-momentum entanglement of photon pairs produced by parametric down-conversion has found several uses in quantum information science, however, it is not suitable for applications involving long-distance propagation as the entanglement decays very rapidly when photons propagate away from their source. Entanglement is lost after a few centimetres of propagation, and the effect becomes even more pronounced in turbulent environments. In contrast, in this article, we show that entanglement in the angle-orbital angular momentum (OAM) bases exhibits a remarkably different behaviour. As with the position-momentum case, initially, the angle-OAM entanglement decays with propagation, but as the photons continue to travel further from the source, the photons regain their strongly correlated behaviour, and the entanglement returns. We theoretically and experimentally demonstrate this behaviour and show that entanglement returns even in the presence of strong turbulence. The only effect of turbulence is to increase the propagation distance for revival, but once revived, the two photons remain entangled up to an arbitrary propagation distance. This work highlights the role that OAM-angle entanglement will play in applications where quantum information is shared over long distances.

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