Secrecy capacity in the four-state protocol of quantum key distribution
Howard E. Brandt · Journal of Mathematical Physics · 2002
The process of key distillation from the quantum transmission in quantum key distribution is reviewed, with the objective of calculating the secrecy capacity of the four-state protocol in the presence of an individual attack in which the eavesdropping probe is entangled with the signal states, and states of the probe become correlated with the states measured by the legitimate receiver. Emphasis is placed on information leakage to the eavesdropping probe. The calculation generalizes earlier work to include an arbitrary angle between the signal bases.