Chengfang Ge

Asynchronous measurement-device-independent quantum key distribution (AMDI-QKD) stands out for its experimental simplicity and high key rate generation. To simplify the system further, we devise a post-measurement compensation scheme to accurately estimate the mutual frequency offset between two compact lasers using just the announced quantum-signal detection results, thereby obviating the need for optical reference light. As a result, we demonstrate an AMDI-QKD system operating at 2.5 GHz and achieving secure key rates (SKRs) of 537 and 101 kbit/s at distances of 100 and 201 km, respectively. By leveraging ultra-stable lasers, we achieve the highest SKRs with measurement-device-independent security within the 100 to 400 km range.

A post-measurement coincidence pairing technique is proposed to hold a repeater-like advantage and simultaneously mitigate the global phase tracking. Here, we demonstrate a practical asynchronous MDI-QKD system with an excellent long-term stability. With the use of two independent economical acetylene-stabilized fiber lasers, we achieve a secure key rate (SKR) of 14.65 bit/s over 504 km fiber, beating the absolute repeaterless bound by 1.18 times. Our work will advance the development of economical and efficient quantum network.

Quantum fingerprinting (QF) enables exponential reduction of information transmission in communication complexity tasks. Coherent QF implementations rely upon a direct optical link to maintain coherence between the users, violating the no-shared-randomness rule. Here, we propose and experimentally demonstrate a novel QF protocol based on asynchronous coincidence pairing from the interference results between independent, remotely prepared coherent fields. Over a length of 20 km telecom fiber, our setup has outperformed the classical algorithm, for the first time without being susceptible to shared randomness. This work advances the practical application of QF in communication complexity.