  We simplified our previously proposed quantum bit commitment (QBC) protocol
based on the Mach-Zehnder interferometer, by replacing symmetric beam splitters
with asymmetric ones. It eliminates the need for random sending time of the
photons; thus, the feasibility and efficiency are both improved. The protocol
is immune to the cheating strategy in the Mayers-Lo-Chau no-go theorem of
unconditionally secure QBC, because the density matrices of the committed
states do not satisfy a crucial condition on which the no-go theorem holds.
