Experimental Side Channel Analysis of BB84 QKD Source

A typical implementation of BB84 protocol for quantum communication uses four laser diodes transmitting weak coherent pulses, which may not have the same characteristics. We characterized these lasers mismatch in various parameters such as spectral width, pulse spatial mode, peak wavelength, polarization and their arrival times at receiver. This information is utilized to calculate possible leakage through side channel attacks by evaluating mutual between source eavesdropper. Based on our experimental observations cross correlation parameter values different diodes, we suggest methods reduce Eve.