# Visibility

The following command changes the mode of the machine to the visibility mode in which the visibility of a unitary transformation can be calculated:
visibility mode;
The visibility of a quantum state with respect to a unitary transformation is generally defined as

 (8)

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 are calculated internally after that command. To see the visibility, one types the command:
visibility;
There are other commands related to the visibility. vtrace'' command is to show the matrix ; vphase'' shows the phase .

root
2004-11-07