"A spin heat engine coupled to a harmonic-oscillator flywheel" Mark Mitchison, Trinity College Dublin, Ireland
Dr. Mark Mitchison, Postdoctral Researcher, Trinity College Dublin, Ireland
I will present a recent realisation of a heat engine comprising a single trapped ion , focussing on the theoretical underpinnings of this experiment. The ion’s spin constitutes the engine’s working medium, while its quantised vibrations act as the load, or “flywheel”, which captures the output work. Characterising the flywheel’s Husimi Q function allows us to measure the mechanical work output of a heat engine with single-quantum resolution for the first time. The measurements reveal the random character of the energy transferred to the flywheel, due to unavoidable thermal fluctuations. I will explain how the ergotropy — a key quantity in quantum thermodynamics — helps us to distinguish between useful work and useless thermal energy by examining the flywheel’s quantum state. The results elucidate how fluctuations fundamentally limit engine performance at the nanoscale.
 D. von Lindenfels et al., Phys. Rev. Lett. 123, 080602 (2019)