Quantum Process Estimation via Generic Two-Body Correlations

TL;DR

This paper introduces a framework for quantum process estimation using generic correlations, enabling accurate quantum dynamics reconstruction even with faulty devices and minimal data processing overhead.

Contribution

It generalizes existing quantum process tomography methods to incorporate imperfect devices and classical correlations, improving robustness and practicality.

Findings

Classical correlations suffice for full system identification in noisy settings.

Optimal input states minimize error amplification during inversion.

The method applies to quantum tomography with faulty state generators and analyzers.

Abstract

Performance of quantum process estimation is naturally limited to fundamental, random, and systematic imperfections in preparations and measurements. These imperfections may lead to considerable errors in the process reconstruction due to the fact that standard data analysis techniques presume ideal devices. Here, by utilizing generic auxiliary quantum or classical correlations, we provide a framework for estimation of quantum dynamics via a single measurement apparatus. By construction, this approach can be applied to quantum tomography schemes with calibrated faulty state generators and analyzers. Specifically, we present a generalization of "Direct Characterization of Quantum Dynamics" [M. Mohseni and D. A. Lidar, Phys. Rev. Lett. 97, 170501 (2006)] with an imperfect Bell-state analyzer. We demonstrate that, for several physically relevant noisy preparations and measurements, only classical correlations and small data processing overhead are sufficient to accomplish the full system identification. Furthermore, we provide the optimal input states for which the error amplification due to inversion on the measurement data is minimal.