Statistics of the quantized microwave electromagnetic field in mesoscopic elements at low temperature

TL;DR

This paper explores the quantum properties of microwave electromagnetic fields in mesoscopic systems at low temperatures, emphasizing the importance of reducing thermal noise to observe nonclassical effects linked to charge quantization.

Contribution

It provides a detailed analysis of the statistical properties of quantized microwave fields in mesoscopic elements, connecting charge transport to photon emission at quantum noise levels.

Findings

Thermal noise can be suppressed to observe quantum effects.

Discrete charge transport correlates with photon emission.

Microwave field statistics reveal nonclassical behavior.

Abstract

The quantum behaviour of the electromagnetic field in mesoscopic elements is intimately linked to the quantization of the charge. In order to probe nonclassical aspects of the field in those elements, it is essential that thermal noise be reduced to the quantum level, i.e. to scales where kT < h{\nu}. This is easily achieved in dilution refrigerators for frequencies of a few GHz, i.e. in the microwave domain. Several recent experiments have highlighted the link between discrete charge transport and discrete photon emission in simple mesoscopic elements such as a tunnel junction. Photocount statistics are inferred from the measurement of continuous variables such as the quadratures of the field.