Temperature as a quantum observable

Abstract

In this article, we address the problem of how temperature of a quantum system is observed. By proposing a thought experiment, we argue that temperature must be conceived as an operator and its measurement must necessarily accompany a collapse in the wavefunction. We model a temperature measurement device and determine the expectation value and quantum uncertainty of its readout. Lastly, we explore the consequences of this point of view and propose an experiment to verify if temperature is indeed a quantum observable.

v3: added new section on position thermometers and several minor corrections