  It is shown that the fault testing for quantum circuits does not follow
conventional classical techniques. If probabilistic gate like Hadamard gate is
included in a circuit then the classical notion of test vector is shown to
fail. We have reported several new and distinguishing features of quantum fault
and also presented a general methodology for detection of functional faults in
a quantum circuit. The technique can generate test vectors for detection of
different kinds of fault. Specific examples are given and time complexity of
the proposed quantum fault detection algorithm is reported.
