Real-time stabilization the bias point of electro-optic amplitude modulator at the single-photon level

Abstract

In a quantum key distribution (QKD) system, it is demanded that electro-optic amplitude modulator (EOAM) must be biased at the minimum point to generate the high extinction ratio (ER) pulses. We present a scheme for real-time stabilization the bias point of EOAM at the single-photon level. By using the single-photon modulation technology, the minimum bias point drift of the EOAM is compensated endlessly and the ER of single-photon pulses remains above 23.4 dB over 5000 s, which could be directly applied for QKD system.