Thermal light cannot be represented as a statistical mixture of single pulses

TL;DR

This paper demonstrates that thermal light cannot be accurately represented as a mixture of single broadband coherent pulses, as such mixtures fail to reproduce key correlation functions of thermal light.

Contribution

It proves the limitations of representing thermal light with single pulses and constructs a modified mixture that matches first-order but not second-order correlations.

Findings

Mixtures of single broadband coherent pulses cannot reproduce thermal light.

A modified mixture can match the first-order correlation function.

Such mixtures fail to reproduce the second-order correlation function.

Abstract

We ask whether or not thermal light can be represented as a mixture of single broadband coherent pulses. We find that it cannot. Such a mixture is simply not rich enough to mimic thermal light; indeed, it cannot even reproduce the first-order correlation function. We show that it is possible to construct a modified mixture of single coherent pulses that does yield the correct first-order correlation function at equal space points. However, as we then demonstrate, such a mixture cannot reproduce the second-order correlation function.