Experimental demonstration of the DPTS QKD protocol over a 170 km fiber link

Quantum key distribution (QKD) is a promising technology that aims to solve the security problem arising from the advent of quantum computers. While the main theoretical aspects are well developed today, limited performances, in terms of the achievable link distance and the secret key rate, are preventing the deployment of this technology on a large scale. More recent QKD protocols, which use multiple degrees of freedom for encoding of the quantum states, allow enhancement of the system performances. Here, we present the experimental demonstration of the differential phase-time shifting protocol up to 170 km of the fiber link. We compare its performance with the well-known coherent one-way and differential phase shifting protocols, demonstrating a higher secret key rate up to 100 km. Moreover, we propagate a classical signal in the same fiber, proving the compatibility of quantum and classical light.