Experimental demonstration of 4-state reference-frame-independent quantum key distribution over 200km

TL;DR

This paper introduces a 4-state reference-frame-independent quantum key distribution protocol that simplifies implementation while maintaining comparable security and distance performance to the original 6-state protocol, demonstrated over 200 km.

Contribution

The authors propose a novel 4-state RFI-QKD protocol that reduces system complexity and is experimentally validated over 200 km, matching the performance of the 6-state protocol.

Findings

4-state RFI protocol achieves similar secure key rate as 6-state protocol.

Experimental demonstration over 200 km confirms feasibility.

Reduced quantum states simplify practical implementation.

Abstract

Reference frame independent quantum key distribution (RFI-QKD) has gained widespread attention due to the unique advantage for practical application, as it circumvents the need for active reference frame alignment within the system. However, in comparison to the standard BB84 protocol, the original 6-state RFI protocol requires a greater number of quantum states to be operated by Alice and Bob, which is an aspect that merits optimization. In this work, we propose a 4-state RFI protocol and illustrate that Alice and Bob each require only four quantum states to perform channel estimation that remains independent of reference frame deviation, which can proficiently reduce the system complexity. Furthermore, through numerical simulations taking the finite-size key effect into consideration, we show that 4-state RFI protocol can achieve a secure key rate and transmission distance on par with the original 6-state RFI protocol. Finally, a experiment over 200 km is inplemented to conducted the feasibility of our scheme. We believe that our protocol can streamline the implementation of RFI-QKD and thereby contribute to the practical advancement of RFI-QKD.