Nonequilibrium Fluctuations: Today, cutting-edge technology allows us to access, manipulate, and build incredibly small engines, from the molecular motors operating inside cells to the artificial molecular machines they inspire. At such small scales, the world is very different from our everyday experience: fluctuations dominant and inertia is irrelevant. Using tools of stochastic thermodynamics and fluctuation theorems, I have been working to understand how energy dissipation can be used to modulate those fluctuations. We have recently shown that large and rare fluctuations are constrained by the energy dissipation throughout the system. I envision this fundamental relation will serve as a guiding design principle for the operation of nanoscale devices, both artificial and natural.
Information Thermodynamics: Feedback is a powerful tool, allowing one to use microscopic knowledge of a system to control it. With the recent advances in our ability to interrogate and modify the dynamics of mesoscopic systems, assessing the energetic constraints of such control is paramount. By developing a new fluctuation theorem, I have shown that in the presence of feedback the second law of thermodynamics is modified by the inclusion of a term measuring the information gained in a measurement. This information is a thermodynamic resource allowing one to enhance the energetic output of thermodynamic engines using feedback. It also constrains the energetic requirements of measurement and sensing. Such insights hold promise for revealing the minimal requirements for sensing, measurement, and decision making in organisms, such as bacteria, that must monitor and respond to their environment.
Quantum Thermodynamics: Quantum coherences are a unique thermodynamic resource, offering the possibilty of quantum-boosted thermodynamic engines. In trying to unravel the role of quantum effects in thermodynamics, I have been working to develop a quantum stochastic thermodynamics that consistently describes quantum fluctuations of thermodynamic quantities -- such as work, heat and entropy -- along individual quantum trajectories. I have applied this technique to study work and heat fluctuations in quantum systems coupled to thermal environments as well as more general environments modeled as completely-postiive trace-preserving maps. This work reveals that quantum coherences manifest themselves as a novel thermodynamic force that can be exploited as an alternative free energy source.