Observation of Squeezing in the Electron Quantum Shot Noise of a Tunnel Junction

TL;DR

This paper demonstrates quantum squeezing in the electromagnetic field emitted by a tunnel junction, confirming its quantum nature through measurements of field fluctuations below vacuum levels.

Contribution

First observation of squeezing in the electromagnetic field from a quantum conductor, revealing its quantum properties via fluctuation measurements.

Findings

Quadrature fluctuations can be below vacuum level.

Electromagnetic field from a tunnel junction exhibits quantum squeezing.

Confirms the quantum nature of radiation from quantum conductors.

Abstract

We report the measurement of the fluctuations of the two quadratures of the electromagnetic field generated by a quantum conductor, a dc- and ac-biased tunnel junction placed at very low temperature.We observe that the variance of the fluctuations on one quadrature can go below that of vacuum, i.e., that the radiated field is squeezed. This demonstrates the quantum nature of the radiated electromagnetic field.