Irreversibility of heat transport and optical non-coherence: an experimental demonstration of the analogy

The arrow of time problem remains one of the most intriguing questions of modern physics. We investigate one particular example of this problem: the irreversibility of heat transfer through an interface between two materials. This special case turned out to be much simpler than that of transport phenomena in bulk materials. We start by exploring a mechanism that turns equations of reversible, unitary transmission of wave-particles through the interface into irreversible equations, describing the distribution functions at the interface. This mechanism, non-coherence, is treated in an analogy with wave optics: no real waves are absolutely monochromatic and thus have finite temporal coherence. We find an experimental setup to prove the suggested mechanism and calculate the optimal parameters to observe the phenomenon. We conduct an experiment whose results fully agree with the predictions of our theory. In the final discussion, we revisit the connection with heat transport through a material interface and show that only the suggested mechanism can explain the irreversibility of interfacial transport.