Variational Quantum Algorithm for Conditional Thermal State Generation

Measuring the temperature of quantum systems with high accuracy remains a significant challenge. In Quantum Sci. Technol. 9, 045018 (2024), the concept of a conditional thermal state, which is a generalized thermal state conditioned on the pointer states of a given measurement apparatus, was introduced and shown to outperform the conventional Gibbs state in low-temperature quantum thermometry. In this talk, we present a method for preparing the conditional thermal state using variational quantum algorithms that can be implemented on NISQ devices.