  Detecting and isolating faults is crucial for synthesis of quantum circuits.
Under the single fault assumption that is now routinely accepted in circuit
fault analysis, we show that the behaviour of faulty quantum circuits can be
fully characterized by the single faulty gate and the corresponding fault
model. This allows us to efficiently determine test input states as well as
measurement strategy that can be used to detect every single-gate fault using
very few test cases and with minimal probability of error; in fact we
demonstrate that most commonly used quantum gates can be isolated without any
error under the single missing gate fault (SMGF) model. We crucially exploit
the quantum nature of circuits to show vast improvement upon the existing works
of automatic test pattern generation (ATPG) for quantum circuits.
