Composably secure time-frequency quantum key distribution

Understand

We present a composable security proof, valid against arbitrary attacks and including finite-size effects, for a high dimensional time-frequency quantum key distribution (TFQKD) protocol based upon spectrally entangled photons.

• Previous works have focused on TFQKD schemes as it combines the impressive loss tolerance of single-photon QKD with the large alphabets of continuous variable (CV) schemes, which enables the potential for more than one bit of secret key per transmission.
• However, the finite-size security of such schemes has only been proven under the assumption of collective Gaussian attacks.
• Here, by combining recent advances in entropic uncertainty relations for CVQKD with decoy state analysis, we derive a composable security proof that predicts key rates on the order of Mbits/s over metropolitan distances (40km or less) and maximum transmission distances of up to 140km.