Blind calibration of a quantum computer

The calibration of quantum measurements is limited by the ability to accurately prepare quantum states under unknown device errors. We develop an accurate calibration protocol for the measurement apparatus of a quantum computer that is `blind’ to the state preparation. Blind calibration quantifies and corrects measurement errors from simple tomographic data on a noisy quantum state. Importantly, it calibrates multiple error mechanisms in a single experiment, eliminating the need for bespoke, separate calibration experiments. Using a trapped-ion quantum computer, we systematically demonstrate the accuracy of the method. We use blind calibration to estimate the native calibration parameters of the experimental system. The recovered calibrations are consistent with directly measured values and perform similarly in predicting the state properties.

💡 Research Summary

The paper tackles a fundamental obstacle in quantum computing: the calibration of measurement devices in the presence of unknown state‑preparation errors. Traditional approaches assume that either the state preparation or the measurement apparatus is already well‑characterized, and they rely on separate calibration experiments for each error source. The authors introduce a “blind calibration” protocol that removes this assumption, allowing the calibration parameters of the measurement hardware to be inferred directly from tomographic data obtained on an arbitrary, possibly noisy quantum state.

The core idea is to model a mis‑calibrated measurement operator (M(\zeta)) as a function of a set of calibration parameters (\zeta). The observed data (y(\zeta,\rho)=\mathrm{tr}