Calibration of Receiver Noise in CV-QKD Systems

Abstract:
Continuous variable quantum key distribution systems could be a cost-effective way to secure communication in the future, not threatened by increasing computational power. These systems require a reliable estimation of the excess noise power contained in the quantum signal to ensure the security and maximize the key rate and distance. The accuracy of the excess noise estimate is strongly affected by the calibration of the noise power of the coherent receiver. Due to an unavoidable time delay between the calibration and the quantum signal measurement, the receiver noise power estimated by the calibration and that contained in the actual quantum signal may be different. This leads to systematic errors in the excess noise estimate compromising the security or degrading the performance. The accuracy of the receiver noise calibration depend on the measurement time delay is investigated. A maximum allowed time period after which a receiver noise recalibration must be done is defined.