Impact of Third-Order Intermodulation on the Performance of Subcarrier Multiplexed Quantum Key Distribution

This paper extends the analysis presented in a previous contribution to account for the effect of third-order intermodulation distortion in the system quantum bit error rate attainable in subcarrier multiplexed quantum key distribution (SCM-QKD) systems, showing that under practical conditions this effect can be safely neglected. When the unconditionally secure key distribution rate is computed for BB84 SCM-QKD systems based on weak coherent pulses and strong reference, it is found a per-channel additional decrease due to nonlinear distortions as low as 1% when compared to the dedicated nonmultiplexed BB84 key distribution channels operated under the same conditions.