  As Fahmi and Golshani correctly point out, a protocol introduced in A.
Cabello, Phys. Rev. Lett. 85, 5635 (2000), to show that a quantum key
distribution protocol can have efficiency one (i.e., can achieve the Holevo
limit), does indeed not have efficiency one. The corrected protocol, introduced
in A. Cabello, Recent. Res. Devel. Physics 2, 249 (2001), is reproduced here.
