Manipulating photon coherence to enhance the security of practical quantum key distribution

TL;DR

This paper presents the first practical, secure distributed-phase-reference quantum key distribution system that uses a novel light source to control photon coherence, achieving high key rates with simplified hardware.

Contribution

Introduces a secure, modulator-free DPR QKD system with a novel light source, demonstrating practical security and high key rates for real-world applications.

Findings

Achieved megabit per second key rates, nearly three times higher than BB84.

Demonstrated information-theoretic security of a DPR QKD system.

System operates without active stabilization or complex receivers.

Abstract

Quantum key distribution (QKD) allows two users to communicate with theoretically provable secrecy by encoding information on photonic qubits. Current encoders are complex, however, which reduces their appeal for practical use and introduces potential vulnerabilities to quantum attacks. Distributed-phase-reference (DPR) systems were introduced as a simpler alternative, but have not yet been proven practically secure against all classes of attack. Here we demonstrate the first DPR QKD system with information-theoretic security. Using a novel light source, where the coherence between pulses can be controlled on a pulse-by-pulse basis, we implement a secure DPR system based on the differential quadrature phase shift protocol. The system is modulator-free, does not require active stabilization or a complex receiver, and also offers megabit per second key rates, almost three times higher than the standard Bennett-Brassard 1984 (BB84) protocol. This enhanced performance and security highlights the potential for DPR protocols to be adopted for real-world applications.