Experimental Test of the Crooks Fluctuation Theorem in a Single Nuclear Spin

We experimentally test the Crooks fluctuation theorem in a quantum spinsystem. Our results show that the Crooks fluctuation theorem is valid fordifferent speeds of the nonequilibrium processes and under various effectivetemperatures. Work is not an observable in quantum systems, which makes testsof quantum thermodynamic theorems challenging. In this work, we developedhigh-fidelity single-shot readouts of a single nuclear spin in diamond andimplemented the two-point work measurement protocol, enabling a directexperimental test of the Crooks fluctuation theorem. Our results provide aquantum insight into fluctuations and the methods we developed can be utilizedto study other quantum thermodynamic theorems.