Cryptographic key exchange protocols traditionally rely on computational conjectures such as the hardness of prime factorisation to provide security against eavesdropping attacks. Remarkably, quantum key distribution protocols like the one proposed by Bennett and Brassard provide information-theoretic security against such attacks, a much stronger form of security unreachable by classical means. However, quantum protocols realised so far are subject to a new class of attacks exploiting implementation defects in the physical devices involved, as demonstrated in numerous ingenious experiments. Following the pioneering work of Ekert proposing the use of entanglement to bound an adversary's information from Bell's theorem, we present here the experimental realisation of a complete quantum key distribution protocol immune to these vulnerabilities. We achieve this by combining theoretical developments on finite-statistics analysis, error correction, and privacy amplification, with an event-ready scheme enabling the rapid generation of high-fidelity entanglement between two trapped-ion qubits connected by an optical fibre link. The secrecy of our key is guaranteed device-independently: it is based on the validity of quantum theory, and certified by measurement statistics observed during the experiment. Our result shows that provably secure cryptography with real-world devices is possible, and paves the way for further quantum information applications based on the device-independence principle.

翻译：加密关键交换协议传统上依赖于计算假设,例如,主要因素的硬度,以提供防范窃听攻击的安全。值得注意的是,像Bennett和Brassard提议的那样量子关键分配协议,提供了针对这类攻击的信息理论安全,这是一种更强大的安全形式,通过古典手段是无法达到的。然而,迄今为止实现的量子协议受到一种新的攻击,利用了所涉物理装置的实施缺陷,正如许多巧妙实验所显示的那样。Ekert提出使用纠缠于从Bell的理论中捆绑对手信息的创新工作之后,我们在这里介绍了一个实验性实现完整量子关键分配协议,避免了这些脆弱性。我们通过将关于定时统计分析、错误纠正和隐私扩增的理论发展结合起来,同时采用一个备受事件准备的计划,能够迅速产生两个与光纤链接连接的闭合点之间的高度不共性纠缠。我们钥匙的保密性是依靠设备保证的保密性:它是实验性地实现一个完整的量基理论,也是基于我们所观察到的直径测量的方法,这是我们所观察到的直径测量的直径的测量结果。