Chip-based Quantum Key Distribution

Improvement in secure transmission of information is an urgent practical need for governments, corporations and individuals. Quantum key distribution (QKD) promises security based on the laws of physics and has rapidly grown from proof-of-concept to robust demonstrations and even deployment of commercial systems. Despite these advances, QKD has not been widely adopted, and practical large-scale deployment will likely require integrated chip-based devices for improved performance, miniaturisation and enhanced functionality, fully integrated into classical communication networks. Here we report low error rate, GHz clocked QKD operation of an InP transmitter chip and a SiO$_x$N$_y$ receiver chip --- monolithically integrated devices that use state-of-the-art components and manufacturing processes from the telecom industry. We use the reconfigurability of these devices to demonstrate three important QKD protocols --- BB84, Coherent One Way (COW) and Differential Phase Shift (DPS) --- with performance comparable to state-of-the-art. These devices, when combined with integrated single photon detectors, satisfy the requirements at each of the levels of future QKD networks --- from point-of-use through to backbone --- and open the way to operation in existing and emerging classical communication networks.