Security of quantum key distribution with non-I.I.D. light sources

TL;DR

This paper proves the security of a quantum key distribution protocol using practical, non-I.I.D. light sources, addressing real-world deviations from idealized models to ensure secure quantum communication.

Contribution

It establishes security under realistic source assumptions, including phase and intensity fluctuations, regardless of I.I.D. conditions, bridging theory and practical QKD implementations.

Findings

Security holds despite phase and intensity fluctuations.

I.I.D. assumption is not necessary for security.

Practical sources can be securely used in QKD.

Abstract

Although quantum key distribution (QKD) is theoretically secure, there is a gap between the theory and practice. In fact, real-life QKD may not be secure because component devices in QKD systems may deviate from the theoretical models assumed in security proofs. To solve this problem, it is necessary to construct the security proof under realistic assumptions on the source and measurement unit. In this paper, we prove the security of a QKD protocol under practical assumptions on the source that accommodate fluctuation of the phase and intensity modulations. As long as our assumptions hold, it does not matter at all how the phase and intensity distribute nor whether or not their distributions over different pulses are independently and identically distributed (I.I.D.). Our work shows that practical sources can be safely employed in QKD experiments.