Down-conversion of quantum fluctuations of photonic heat current in a circuit

TL;DR

This paper investigates the non-zero frequency noise of heat current carried by thermal photons in a circuit, revealing non-vanishing equilibrium noise at zero temperature and proposing a modulation method to measure high-frequency quantum noise.

Contribution

It introduces a bosonic oscillator model for heat baths that accurately predicts heat current noise and presents a modulation technique to convert high-frequency quantum noise to zero frequency for easier measurement.

Findings

Non-zero frequency heat current noise persists at zero temperature.

The bosonic oscillator model matches conventional results for average heat transport.

A modulation method is proposed to measure high-frequency quantum noise.

Abstract

We discuss the non-zero frequency noise of heat current with the explicit example of energy carried by thermal photons in a circuit. Instead of the standard circuit modelling that gives a convenient way of predicting time-averaged heat current, we describe a setup composed of two resistors forming the heat baths by collections of bosonic oscillators. In terms of average heat transport this model leads to identical results with the conventional one, but besides this, it yields a convenient way of dealing with noise as well. The non-zero frequency heat current noise does not vanish in equilibrium even at zero temperature, the result that is known for, e.g., electron tunneling. We present a modulation method that can convert the difficult-to-measure high frequency quantum noise down to zero frequency.