Independent State and Measurement Characterization on Quantum Computers

Correctly characterizing state preparation and measurement (SPAM) processes is a necessary step towards building reliable quantum processing units (QPUs). In this work, we approach this problem by assuming certain structure on SPAM and gate elements, and derive a simple experimental procedure to separately estimate the SPAM error strengths on a QPU. After discussing principles behind the experimental design, we present the protocol along with an asymptotic bound for the uncertainty in the estimated parameters in terms of quantities that can be estimated independently of SPAM processes. We test this protocol on a publicly available 5-qubit QPU and discuss the applicability of our protocol on near-term devices.