On the general constraints in single qubit quantum process tomography

TL;DR

This paper derives explicit constraints for single-qubit quantum process tomography, enhancing understanding of process matrices and aiding in analyzing errors like qubit leakage.

Contribution

It introduces new explicit forms of constraints for quantum process tomography, providing deeper insights into process matrix structures and error modeling.

Findings

Derived explicit forms of process constraints.

Applied constraints to qubit leakage error models.

Gained intuition on process matrices from examples.

Abstract

We briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These new forms provide additional insight into the structure of the process matrix. We illustrate their utility with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices.