Security of the decoy-state BB84 protocol with imperfect state preparation

TL;DR

This paper analyzes the security of the decoy-state BB84 quantum key distribution protocol considering practical imperfections in source intensity and polarization, supported by experimental characterization.

Contribution

It provides a security analysis of the decoy-state BB84 protocol accounting for source flaws like intensity and polarization imperfections, with experimental validation.

Findings

Security bounds established for imperfect source conditions

Experimental characterization of source fluctuations conducted

Implications for practical QKD implementations discussed

Abstract

The quantum key distribution (QKD) allows two remote users to share a common information-theoretic secure secret key. In order to guarantee the security of a practical QKD implementation, the physical system has to be fully characterized and all deviations from the ideal protocol due to various imperfections of realistic devices have to be taken into account in the security proof. In this work, we study the security of the efficient decoy-state BB84 QKD protocol in the presence of source flaws, caused by imperfect intensity and polarization modulation. We investigate the non-Poissonian photon-number statistics due to coherent-state intensity fluctuations and the basis-dependence of the source due to non-ideal polarization state preparation. The analysis is supported by experimental characterization of intensity and phase distributions.