The Mpemba effect is the counterintuitive phenomenon in statistical physics for which a far-from-equilibrium state can relax toward equilibrium faster than a state closer to equilibrium. This effect has raised a great curiosity since long time and has been studied extensively in many classical and quantum systems. Here it is shown that the Mpemba effect can be observed in optics as well. Specifically, the process of light diffusion in finite-sized photonic lattices under incoherent (dephasing) dynamics is considered. Rather surprisingly, it is shown that certain highly-localized initial light distributions can diffuse faster than initial broadly delocalized distributions. The effect is illustrated by considering random walk of optical pulses in fiber-based temporal mesh lattices, which should provide an experimentally-accessible setup for the demonstration of the Mpemba effect in optics.

Agencia Estatal de Investigacion (MDM-2017-0711).

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