Information Thermodynamics and Fluctuations in Quantum Dots

Abstract: In small systems with large fluctuations, the classical description of thermodynamics is no longer sufficient which has led to the development of stochastic thermodynamics. One important result from stochastic thermodynamics is that with measurement and feedback it is possible to use those fluctuations to extract work from a single heat bath coupled to the system. This is thanks to the connection between information and thermodynamics which is the subject of this thesis. Specifically, dissipation and fluctuations have been experimentally studied for thermodynamic processes involving information using a quantum dot system embedded in an InAs nanowire.Paper I details the fabrication and measurement of double quantum dot devices using the InAs nanowires. Then, in the thesis, the development of real-time readout of the state of the quantum dots using charge sensing is described. In addition, an investigation into the back-action effects of the charge detector was performed.In Paper II, the work fluctuation-dissipation relation was studied for the operation of the resulting device as a Szilard engine which extracts work from the information about the quantum dot charge state. It was found that as the engine's dissipation decreased, so did its fluctuations.The results from Paper III show that it is possible to develop and experimentally implement protocols that minimize the dissipation by modifying the shape of the drive used on the system. Finally, Paper IV investigated a recently discovered thermodynamic uncertainty relation which forces a trade-off between thermodynamic cost and precision. For measurement-feedback scenarios like the Szilard engine, the TUR can be violated unless one also takes into account a time-reversed protocol.