Diamond spins for quantum thermodynamics

Spin-based diamond devices, enabled by exquisite quantum control over long-lived spin states and by tailored interaction with their environment, disclose new possibilities for exploring thermodynamics operating at the nanoscales, where fluctuations and quantum effects play a significant role [1]. Diamond electronic spins allow implementation of both unitary and non-unitary dynamics, involving exchange of work, heat, or both. 

We employed different approaches to quantify the contribution of initial quantum coherence, and nonclassical multi-time correlations in thermodynamic processes. We experimentally demonstrated an end-point measurement approach, in which the statistics of energy-change fluctuations are inferred from knowledge of the initial state and the system Hamiltonian. Using this method, we characterized the entropy production associated to quantum coherence in a driven open quantum system [2]. 

Furthermore, we investigated genuinely nonclassical multi-time correlations in a diamond spin qutrit under a unitary quantum work process, via Kirkwood-Dirac quasiprobability (KDQ) distributions [3]. We measured the real part of KDQ via projective measurements, and the full distribution with an interferometric scheme. Interestingly, we observed anomalous work extraction [4] and analyzed the behavior of the first and second moments of work, connecting them with Robertson-Schrödinger uncertainty relation [5].