  Entropy production is a fundamental concept that plays a crucial role in the
second law of thermodynamics and the measure of irreversibility. It imposes
rigorous constraints on the kinds of transformations allowed in thermodynamic
processes. Using an optical setup, here we experimentally demonstrate the
division of entropy production of an open quantum system into a
population-related component and a coherence-related component, validating
previous theoretical predictions. The coherence-related component represents a
genuine quantum contribution with no classical counterpart. By adjusting bath
temperatures and initial coherences of the system, we first derive the total
entropy production due to both populations and coherences, then remove all the
coherences of the system to solely obtain the population-related contribution.
The difference between these two results permits to isolate the
coherence-related term. Based on this division, our experiment ultimately
proves that irreversibility at the quantum level can be reduced through
properly harnessing the two contributions to entropy production.
