Experimental investigation of coherence contributions to a nonequilibrium thermodynamic process in a driven quantum system

The work done when a system at thermal equilibrium is externally driven by a unitary control parameter leads to irreversible entropy production. The entropy produced can be thought of as a combination of coherence generation and a population mismatch between the target equilibrium state and the actually achieved final state. We experimentally explored this out-of-equilibrium process in an NMR quantum processor and studied the contribution of coherence to irreversible entropy generation. We verified a generalized Clausius inequality, which affirms that irreversible entropy production is lower-bounded.