We propose and experimentally demonstrate a new scheme for measuring high-dimensional phase states using a two-photon interference technique, which we refer to as quantum-controlled measurement. Using this scheme, we implement a d-dimensional time-phase quantum key distribution (QKD) system and achieve secret key rates of 5.26 and 8.65 Mbps using d=2 and d=8 quantum states, respectively, for a 4~dB channel loss, illustrating that high-dimensional time-phase QKD protocols are advantageous for low-loss quantum channels. This work paves the way for practical high-dimensional QKD protocols for metropolitan-scale systems. Furthermore, our results apply equally well for other high-dimensional protocols, such as those using the spatial degree-of-freedom with orbital angular momentum states being one example.
@article{arxiv.1902.00811,
title = {Scalable high-rate, high-dimensional quantum key distribution},
author = {Nurul T. Islam and Charles Ci Wen Lim and Clinton Cahall and Bing Qi and Jungsang Kim and Daniel J. Gauthier},
journal= {arXiv preprint arXiv:1902.00811},
year = {2020}
}