We introduce a self-consistent tomography for arbitrary quantum non-demolition (QND) detectors. Based on this, we build a complete physical characterization of the detector, including the measurement processes and a quantification of the fidelity, ideality, and back-action of the measurement. This framework is a diagnostic tool for the dynamics of QND detectors, allowing us to identify errors, and to improve their calibration and design. We illustrate this on a realistic Jaynes-Cummings simulation of superconducting qubit readout. We characterize non-dispersive errors, quantify the back-action introduced by the readout cavity, and calibrate the optimal measurement point.
@article{arxiv.2109.06616,
title = {Complete physical characterization of QND measurements via tomography},
author = {L. Pereira and J. J. García-Ripoll and T. Ramos},
journal= {arXiv preprint arXiv:2109.06616},
year = {2022}
}