Fakultät für Physik, Ludwig-Maximilians-Universität, München, Germany.
Munich Center for Quantum Science and Technology (MCQST), München, Germany.
Nature. 2022 Jul;607(7920):687-691. doi: 10.1038/s41586-022-04891-y. Epub 2022 Jul 27.
Device-independent quantum key distribution (DIQKD) enables the generation of secret keys over an untrusted channel using uncharacterized and potentially untrusted devices. The proper and secure functioning of the devices can be certified by a statistical test using a Bell inequality. This test originates from the foundations of quantum physics and also ensures robustness against implementation loopholes, thereby leaving only the integrity of the users' locations to be guaranteed by other means. The realization of DIQKD, however, is extremely challenging-mainly because it is difficult to establish high-quality entangled states between two remote locations with high detection efficiency. Here we present an experimental system that enables for DIQKD between two distant users. The experiment is based on the generation and analysis of event-ready entanglement between two independently trapped single rubidium atoms located in buildings 400 metre apart. By achieving an entanglement fidelity of [Formula: see text] and implementing a DIQKD protocol with random key basis, we observe a significant violation of a Bell inequality of S = 2.578(75)-above the classical limit of 2-and a quantum bit error rate of only 0.078(9). For the protocol, this results in a secret key rate of 0.07 bits per entanglement generation event in the asymptotic limit, and thus demonstrates the system's capability to generate secret keys. Our results of secure key exchange with potentially untrusted devices pave the way to the ultimate form of quantum secure communications in future quantum networks.
设备无关量子密钥分发(DIQKD)使得能够在使用未经表征且可能不可信的设备的不可信信道上生成密钥。设备的正确和安全运行可以通过使用贝尔不等式的统计测试来验证。该测试源自量子物理学的基础,并且还确保了对实现漏洞的稳健性,从而仅将用户位置的完整性保留为其他手段来保证。然而,DIQKD 的实现极具挑战性-主要是因为很难在两个远程位置之间建立具有高检测效率的高质量纠缠态。在这里,我们提出了一种实验系统,该系统能够在两个遥远的用户之间进行 DIQKD。该实验基于两个独立囚禁的单个铷原子之间的事件准备型纠缠的产生和分析,这两个原子分别位于相距 400 米的建筑物中。通过实现纠缠保真度为 [Formula: see text] 并实现具有随机密钥基的 DIQKD 协议,我们观察到 S = 2.578(75)-超过经典极限 2-以及量子比特错误率仅为 0.078(9)的明显违反贝尔不等式。对于该协议,这导致在渐近极限下每个纠缠产生事件的秘密密钥率为 0.07 位,从而证明了该系统生成秘密密钥的能力。我们使用潜在不可信设备进行安全密钥交换的结果为未来量子网络中的最终形式的量子安全通信铺平了道路。