Ranni Antti, Brange Fredrik, Mannila Elsa T, Flindt Christian, Maisi Ville F
NanoLund and Solid State Physics, Lund University, Box 118, 22100, Lund, Sweden.
Department of Applied Physics, Aalto University, 00076, Aalto, Finland.
Nat Commun. 2021 Nov 4;12(1):6358. doi: 10.1038/s41467-021-26627-8.
Controlled generation and detection of quantum entanglement between spatially separated particles constitute an essential prerequisite both for testing the foundations of quantum mechanics and for realizing future quantum technologies. Splitting of Cooper pairs from a superconductor provides entangled electrons at separate locations. However, experimentally accessing the individual split Cooper pairs constitutes a major unresolved issue as they mix together with electrons from competing processes. Here, we overcome this challenge with the first real-time observation of the splitting of individual Cooper pairs, enabling direct access to the time-resolved statistics of Cooper pair splitting. We determine the correlation statistics arising from two-electron processes and find a pronounced peak that is two orders of magnitude larger than the background. Our experiment thereby allows to unambiguously pinpoint and select split Cooper pairs with 99% fidelity. These results open up an avenue for performing experiments that tap into the spin-entanglement of split Cooper pairs.
对空间分离的粒子之间的量子纠缠进行可控的产生和探测，是检验量子力学基础和实现未来量子技术的一个基本前提条件。从超导体中分离库珀对可在不同位置提供纠缠电子。然而，实验上获取单个分离的库珀对是一个主要的未解决问题，因为它们会与来自竞争过程的电子混合在一起。在此，我们通过首次实时观测单个库珀对的分裂克服了这一挑战，从而能够直接获取库珀对分裂的时间分辨统计信息。我们确定了双电子过程产生的关联统计信息，并发现一个比背景大两个数量级的明显峰值。我们的实验从而能够以99%的保真度明确地精确识别和选择分离的库珀对。这些结果为开展利用分离库珀对的自旋纠缠的实验开辟了一条途径。
