Impact of BB84 QKD Transmitter’s Wavelength Mismatch on Secure Key Generation Rate

In principle BB84 protocol supports secure quantum communication by assuming transmitter and receiver devices to be ideal. However, practically it is very challenging to build an ideal single photon source and detector. These imperfections in practical devices (i.e., wavelength mismatch, full width at half maximum (FWHM) pulse width mismatch and different arrival times of photon) leads to side channel attacks. In this work, we have analyzed the wavelength mismatch issue associated with four laser diode based practical BB84 transmitter. An asymptotically achievable rate of extraction of secure key (also known as key generation rate) is estimated from side-channel leakage calculation between transmitter (Alice) and adversary (Eve).