Massimo Borghi

We demonstrate an entanglement-based quantum key distribution (QKD) system employing frequency-bin encoding. The entangled state is generated using two independent high-finesse ring resonators fabricated on a silicon photonic chip. The system implements the BBM92 protocol with a passive basis selection scheme and enables simultaneous acquisition of sixteen projective measurements across two mutually unbiased bases. To counteract random phase fluctuations induced by thermal instabilities in the transmission fiber, we apply a real-time adaptive phase correction to the measurement basis. We achieve stable QKD over a 26 km fiber spool with a secure key rate exceeding 4.5 bit/s.

In this work we report the first chip-to-chip multidimensional entanglement distribution. The faithful generation and transmission of the multidimensional quantum states relies on two main ingredients: silicon integrated photonics, offering a compelling platform for quantum information processing, and multicore fibres, which allows the reliable transmission of path encoded qudits.