Security framework for quantum key distribution with imperfect sources

Imperfect bit-and-basis encoders compromise the security of quantum key distribution (QKD) systems via modulation flaws, side channels, and inter-pulse correlations, which invalidate standard security proofs. Existing results addressing such imperfections suffer from critical limitations: they either consider only specific flaws, offer an unreasonably poor performance, or require the protocol to be run very slowly. Here, we present a finite-key security proof approach against coherent attacks that incorporates general bit-and-basis encoding imperfections (including modulation flaws, side channels, and inter-pulse correlations) while achieving significantly better performances than previous approaches and requiring only partial characterization.