Quantum circuit debugging and sensitivity analysis via local inversions

As the width and depth of quantum circuits implemented by state-of-the-art quantum processors rapidly increase, circuit characterization via classical simulation is becoming unfeasible. Thus, it is crucial to develop new methods to identify significant error sources in large and complex quantum circuits. In this work, we present a technique that identifies the layers of a circuit that affect the circuit output the most, and thus helps to identify the most significant sources of error. The technique requires no classical verification of circuit output and is thus a scalable tool for debugging large quantum programs in the form of circuits. We demonstrate the practicality and efficacy of the proposed technique by applying it to example algorithmic circuits implemented on IBM quantum machines.Comment: Theory discussion refined and presentation streamlined in v