The following command changes the mode of the machine to the
visibility mode in which the visibility of a unitary
transformation can be calculated:
The visibility of a quantum state with respect to a unitary
transformation is generally defined as
No sooner the command ``visibility mode'' is input than the current
state is copied to the state . The subsequent quantum gates
is applied to without as well as to
with ( is the state for ordinary calculation),
that is to say, both and
internally after that command.
To see the visibility, one types the command:
There are other commands related to the visibility.
``vtrace'' command is to show the matrix
; ``vphase'' shows the