Experimental Quantum Digital Signature over 102 km

TL;DR

This paper demonstrates a practical quantum digital signature protocol over 102 km of optical fiber without secure channels, marking a significant step towards real-world quantum communication security.

Contribution

The authors experimentally implement a secure quantum digital signature protocol over unprecedented distances without relying on secure channels, using decoy state modulation.

Findings

Successfully signed a 1-bit message over 102 km fiber

Signed a 32-bit message at 51 km distance

Paves the way for practical quantum digital signatures

Abstract

Quantum digital signature (QDS) is an approach to guarantee the nonrepudiation, unforgeability and transferability of a signature with the information-theoretical security. All previous experimental realizations of QDS relied on an unrealistic assumption of secure channels and the longest distance is only several kilometers. Here, we have experimentally demonstrated a recently proposed QDS protocol without any secure channel. Exploiting the decoy state modulation, we have successfully signed one bit message through up to 102 km optical fiber. Furthermore, we continuously run the system to sign the longer message "USTC" with 32 bit at the distance of 51 km. Our results pave the way towards the practical application of QDS.