Boosting the secret key rate in a shared quantum and classical fibre communication system

During the last 20 years, the advance of communication technologies has generated multiple exciting applications. However, classical cryptography, commonly adopted to secure current communication systems, can be jeopardised by the advent of quantum computers. Quantum key distribution (QKD) is a promising technology aiming to solve such a security problem. Unfortunately, current implementations of QKD systems show relatively low key rates, demand low channel noise and use ad hoc devices. In this work, we picture how to overcome the rate limitation by using a 37-core fibre to generate 2.86 Mbit s−1 per core that can be space multiplexed into the highest secret key rate of 105.7 Mbit s−1 to date. We also demonstrate, with off-the-shelf equipment, the robustness of the system by co-propagating a classical signal at 370 Gbit s $${}^{-1}$$ , paving the way for a shared quantum and classical communication network. Quantum key distribution allows ultimate security based on laws of physics, and its integration on the existing optical network is of worldwide interest. Exploiting the concept of space division multiplexing in a 37-cores multicore fibre, this work demonstrates efficient secret key generation and high compatibility with classical communication.