标题： 量子密码学中超越QKD的单光子优势 显示英文标题

标题： Single-Photon Advantage in Quantum Cryptography Beyond QKD

摘要： 在量子密码学中，利用量子物理的基本定律来增强密码任务的安全性。 量子密钥分发到目前为止是最被广泛研究的协议，它使得可信方之间能够建立一个秘密密钥。 然而，在通信网络中存在许多实际应用场景，这些场景也涉及不信任环境中的各方。 在这样的不信任环境中，最基本的量子密码构建块是量子掷硬币，与它的经典对应物相比具有优势。 迄今为止，关于量子掷硬币的实验研究很少，所有研究都使用了概率量子光源，面临基本限制。 在这里，我们通过使用单光子态实验实现了量子强掷硬币协议，并展示了相对于经典实现和使用微弱激光脉冲的实现的优势。 我们通过采用基于半导体量子点的Purcell增强发射的最先进的确定性单光子源，结合快速偏振态编码，实现了低于3%的量子比特错误率，这是协议成功执行所必需的。 减少的多光子发射相比于衰减激光实现，在模拟和实验中都使掷硬币协议的偏差更小。 通过在QKD之外的密码原语中展示单光子量子优势，我们的工作代表了在未来量子互联网中实现复杂密码任务的重大进展。 显示英文摘要

摘要： In quantum cryptography, fundamental laws of quantum physics are exploited to enhance the security of cryptographic tasks. Quantum key distribution is by far the most studied protocol to date, enabling the establishment of a secret key between trusted parties. However, there exist many practical use-cases in communication networks, which also involve parties in distrustful settings. The most fundamental quantum cryptographic building block in such a distrustful setting is quantum coin flipping, which provides an advantage compared to its classical equivalent. So far, few experimental studies on quantum coin flipping have been reported, all of which used probabilistic quantum light sources facing fundamental limitations. Here, we experimentally implement a quantum strong coin flipping protocol using single-photon states and demonstrate an advantage compared to both classical realizations and implementations using faint laser pulses. We achieve this by employing a state-of-the-art deterministic single-photon source based on the Purcell-enhanced emission of a semiconductor quantum dot in combination with fast polarization-state encoding enabling a quantum bit error ratio below 3%, required for the successful execution of the protocol. The reduced multi-photon emission yields a smaller bias of the coin flipping protocol compared to an attenuated laser implementation, both in simulations and in the experiment. By demonstrating a single-photon quantum advantage in a cryptographic primitive beyond QKD, our work represents a major advance towards the implementation of complex cryptographic tasks in a future quantum internet.