Energetic cost of measurements using quantum, coherent, and thermal light

TL;DR

This paper compares the efficiency and thermodynamic costs of quantum, coherent, and thermal light in quantum measurements within circuit QED, revealing thermal light's comparable performance to coherent light and the energy efficiency of single-photon light.

Contribution

It provides a comparative analysis of measurement backaction, signal-to-noise ratio, and thermodynamic costs for different light states in quantum measurements.

Findings

Thermal light performs comparably to coherent light in quantum measurements.

Single-photon light outperforms others in energy cost per information gain.

Single-photon measurements reach the fundamental thermodynamic limit.

Abstract

Quantum measurements are basic operations that play a critical role in the study and application of quantum information. We study how the use of quantum, coherent, and classical thermal states of light in a circuit quantum electrodynamics setup impacts the performance of quantum measurements, by comparing their respective measurement backaction and measurement signal to noise ratio per photon. In the strong dispersive limit, we find that thermal light is capable of performing quantum measurements with comparable efficiency to coherent light, both being outperformed by single-photon light. We then analyze the thermodynamic cost of each measurement scheme. We show that single-photon light shows an advantage in terms of energy cost per information gain, reaching the fundamental thermodynamic cost.