  The practical realizations of BB84 quantum key distribution protocol using
single-photon or weak coherent states have normally presented low efficiency,
in the meaning that most bits sent by Alice are not useful for the final key.
In this work, we show an optical setup to improve the transmission rate of
useful bits putting together two ideas, parallel quantum key distribution and
physical encryption using mesoscopic coherent states. The final result is a
four time faster quantum key distribution setup.
