Process Tomography for Systems in a Thermal State

TL;DR

This paper introduces a process tomography method leveraging temporal correlations, enabling characterization of systems in mixed or thermal states without requiring state preparation or tomography.

Contribution

The method provides a novel approach to process tomography applicable to thermal and mixed states, expanding the tools for quantum system analysis.

Findings

Effective for systems in thermal states

Applicable to Gaussian channels and qubit dynamics

Does not require state preparation or tomography

Abstract

We propose a new method for implementing process tomography that is based on the information extracted from temporal correlations between observables, rather than on state preparation and state tomography. As such, the approach is applicable to systems that are in a mixed state, and in particular to thermal states. We illustrate the method for an arbitrary evolution described by Kraus operators, as well as for simpler cases such as a general Gaussian channels, and qubit dynamics.