QKD STATION WITH EMI SIGNATURE SUPPRESSION

摘要

Methods and systems for suppressing the electromagnetic interference (EMI) signature (R3) generated by a QKD station (Alice) are disclosed. One of the methods includes generating two or more modulator drive signals (S3A, S3B... S3n) corresponding to two or more of the n possible modulator states (e.g., phase states of 0, TT/2, TT, 3TT/2) of the particular QKD protocol. The modulator drive signals are sent to a random number generation (RNG) unit (30'), which randomly selects one of the two or more modulator drive signals and passes it to the modulator. Another method involves generating two modulator drive signals (S3R and S3F) whose voltage sum is constant. One signal (S3R) is sent to the modulator while the other (S3F) is sent to a circuit-terminating element (MF), which can be a second modulator. The method suppresses the EMI signature associated with individual modulation states. This prevents an eavesdropper from gaining information about the modulator states via the EMI signature (e.g., via antennae Al and/or A2), which information could otherwise yield information about the exchanged key.