Security proof of differential phase shift quantum key distribution in the noiseless case

TL;DR

This paper provides a security proof for differential phase shift quantum key distribution in noiseless conditions, demonstrating its potential for high-speed secure communication with a proven lower bound on key rate.

Contribution

It offers the first unconditional security proof for DPS-QKD against collective attacks in the noiseless case, assuming perfect devices and infinite key size.

Findings

Security proof against collective attacks established

Lower bound of key rate proportional to channel transmission

Proof applicable with threshold detectors

Abstract

Differential phase shift quantum key distribution systems have a high potential for achieving high speed key generation. However, its unconditional security proof is still missing, even though it has been proposed for many years. Here, we prove its security against collective attacks with a weak coherent light source in the noiseless case (i.e. no bit error). The only assumptions are that quantum theory is correct, the devices are perfect and trusted and the key size is infinite. Our proof works on threshold detectors. We compute the lower bound of the secret key generation rate using the information-theoretical security proof method. Our final result shows that the lower bound of the secret key generation rate per pulse is linearly proportional to the channel transmission probability if Bob's detection counts obey the binomial distribution.