Universal Property of Quantum Measurements of Equilibrium Fluctuations and Violation of Fluctuation-Dissipation Theorem

TL;DR

This paper demonstrates that in macroscopic quantum systems, ideal measurements of equilibrium fluctuations always yield symmetrized time correlations, leading to a partial violation of the fluctuation-dissipation theorem.

Contribution

It establishes a universal property of quantum measurements of equilibrium fluctuations and reveals the partial violation of FDT in macroscopic quantum systems.

Findings

Symmetrized time correlation is always obtained in ideal measurements.

FDT is partially violated in macroscopic quantum systems.

Ideal measurement procedures do not fully adhere to classical fluctuation-dissipation relations.

Abstract

For macroscopic quantum systems, we study what are measured when equilibrium fluctuations of macrovariables are measured in an ideal way that mimics classical ideal measurements as closely as possible. We find that the symmetrized time correlation (symTC) is always obtained for such measurements. As an important consequence, we show that the fluctuation-dissipation theorem (FDT) is partially violated as a relation between observed quantities in macroscopic quantum systems even if measurements are made in such an ideal way.