  We investigate quantum repeaters in the context of quantum key distribution.
We optimize the secret key rate per memory per second with respect to different
distillation protocols and distillation strategies. For this purpose, we also
derive an analytical expression for the average number of entangled pairs
created by the quantum repeater, including classical communication times for
entanglement swapping and entanglement distillation. We investigate the impact
of this classical communication time on the secret key rate. We finally study
the effect of the detector efficiency on the secret key rate.
