Optimal Axis Compensation in Quantum Key Distribution Protocols

摘要

We show the optimal axis compensations maximizing the key generation rate for unital channels. We consider the case in which only Bob is allowed to compensate his axis, or the case in which both Alice and Bob are allowed to compensate their axes. We clarify that the optimal key generation rates for two cases coincides if they utilize the mismatched measurement outcomes in the channel estimation. We also clarify that the optimal key generation rates for two cases does not coincide in general if they do not utilize the mismatched measurement outcomes in the channel estimation.