Cheap readout error mitigation on expensive NISQ devices*

Readout error mitigation (REM) is an efficient tool to improve the functionality of Noisy Intermediate-Scale Quantum (NISQ) devices. In most superconducting prototype quantum computers, the readout error dominates the errors of individual gates. The level of improvement gained by REM depends on the error probabilities and number of shots available. In this work, we quantify the efficiency of REM for specific quantum protocols, e.g., quantum state tomography. Considering the scenario where the number of available shots is fixed, we find the optimal distribution of these shots between the REM task and the quantum protocol itself. In a second scenario, we find the minimal number of total shots required to perform the quantum protocol with a fixed target precision. These tasks are of direct financial relevance, since certain quantum computer providers bill after the number of shots executed.