Fig. 1
From: Realistic vulnerabilities of decoy-state quantum key distribution
Eve’s polarization-encoding setup for the USD attack. The depicted distribution of photons corresponds to a conclusive outcome for horizontally polarized state as an example. Det\(_\text {H,V,D,A}\), detectors for horizontal, vertical, diagonal and anti-diagonal polarization; PBS, polarization beam-splitter; BS 50:50, symmetric beam-splitter; \(\lambda /2\), half-wave plate for diagonal basis selection. The same setup can be designed for phase encoding.
