A crucial step in the synthesis of quantum circuits is detection and isolation of faults. However the standard techniques of automatic test pattern generators (ATPG) for classical reversible circuits are not directly applicable to quantum circuits, primarily due to their probabilistic nature. For faulty quantum circuits under the widely accepted single fault assumption, we show that their behaviour can be fully characterised by the single faulty gate and the corresponding fault model. This allows us to efficiently determine test input states as well as measurement strategy for fault detection and diagnosis. Building on top of these, we design randomised algorithms which are able to detect every single-gate fault with minimal probability of error. We also describe similar algorithms for fault diagnosis. We evaluate our algorithms by the number of output samples that needs to be collected and the probability of error. Both of these can be related to the eigenvalues of the operators corresponding to the circuit gates. We experimentally compare all our strategies with the state-of-the-art ATPG techniques for quantum circuits under SMGF model and demonstrate that significant improvement is possible if we can exploit the quantum nature of these circuits.
Format: There is one line for each gate. Each line has this format:
F-gate-id : error = (p0,q0,r0)|(p1,q1,r1)|… where,
Run as: python code.py circuit.txt
Prof. Subhamoy Maitra, ISI Kolkata: For hosting the author during summer 2015 during which the work was initiated.
Prof. Sushanta Chakraborty, IIEST Shibpur, Howrah: For introducing the author to the problem.
Sparsa Roychowdhuri: Some of the initial simulation and experiment code was written by this student and included in a preliminary version