Digital contactless payments have replaced physical banknotes in many aspects of our daily lives. Similarly to banknotes, they are easy to use, unique, tamper-resistant and untraceable, but additionally have to withstand attackers and data breaches in the digital world. Current technology substitutes customers' sensitive data by randomized tokens, and secures the uniqueness of each digital purchase with a cryptographic function, called a cryptogram. However, computationally powerful attacks violate the security of these functions. Quantum technology, on the other hand, has the unique potential to guarantee payment protection even in the presence of infinite computational power. Here, we show how quantum light can secure daily digital payments in a practical manner by generating inherently unforgeable quantum-cryptograms. We implement the full scheme over an urban optical fiber link, and show its robustness to noise and loss-dependent attacks. Unlike previously proposed quantum-security protocols, our solution does not depend on challenging long-term quantum storage or a network of trusted agents and authenticated channels. The envisioned scenario is practical with near-term technology and has the potential to herald a new era of real-world, quantum-enabled security.

翻译：数字非接触支付已在日常生活的许多方面取代了实体纸币。与纸币类似，它们易于使用、具有唯一性、防篡改且不可追踪，此外还必须在数字世界中抵御攻击者和数据泄露。现有技术使用随机化令牌替代客户的敏感数据，并通过一种称为密文的加密函数保障每次数字支付的唯一性。然而，具备强大计算能力的攻击会破坏这些函数的安全性。相比之下，量子技术具有独特潜力，即便在无限计算能力存在的条件下也能确保支付保护。本文展示了如何利用量子光以实用方式通过生成本质上不可伪造的量子密文来保障日常数字支付的安全性。我们在城市光纤链路上实现了完整方案，并证明了其对噪声和依赖损耗的攻击的鲁棒性。与先前提出的量子安全协议不同，我们的解决方案不依赖于具有挑战性的长期量子存储或可信节点网络及认证信道。该构想场景在近未来技术条件下具有实用性，有望开启基于量子技术的现实世界安全新时代。