Information, work, and heat in small systems

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Nearly 150 years ago, James Clerk Maxwell first asked what happens when a "neat-fingered being"-a demon-takes advantage of information to extract useful energy (work) from heat. The Second Law of Thermodynamics should forbid this, but how? The question galled physicists and provoked debate for well over a century. Starting in 2008, my lab developed a new technique for creating and studying such Maxwell demons and related devices for gathering and using relevant information. This feedback trap lets us place a small, micron-scale bead in a potential whose form we can design, essentially at will. This technological advance has led to important scientific applications at the intersection of thermodynamics, nonequilibrium statistical physics, information theory, and control theory, notably a definitive measurement in 2014 that confirms a 60-year-old hypothesis: that Maxwell demons need to erase information and that erasing information requires dissipating as much energy as is gained. The next five years for my research program will focus on three groups of projects: 1. Anomalous cooling and heating.  We recently used our feedback trap to show that a hot system can sometimes cool more quickly than a warm system under identical conditions ("Mpemba effect"). Building on this success, we will investigate a recently proposed anomalous-heating scenario (inverse Mpemba effect) and related questions. 2. Experiments on information and thermodynamics.  We will continue work on information engines, with the overall goal of transforming Maxwell demons from thought experiments raising paradoxes to experimental illustrations of fundamental thermodynamic limits to practical devices that carry out useful tasks. We will optimize the costs of basic computational operations (bit erasure, logic gates) when operated at finite rates and look at new problems where information plays a role, such as the minimum power needed to stabilize an unstable system. 3. Heat flow in single cells.   We will develop new instrumentation for studying heat production from single biological cells. The longer-term motivation is to create a new tool for understanding the dynamics of cellular metabolism-how nutrients are consumed at the single-cell level. The shorter-term goal is to resolve a striking scientific discrepancy, the "105 gap" between predicted and measured intracellular temperature variations. The first two projects directly extend previous (very successful) work in my group. The third is a new direction, with the potential to create a new field (single-cell calorimetry) and resolve one of the outstanding scientific puzzles of our time. The above questions are ones that underlie our understanding of biology and life, as well as engineering at small scales. They will inspire and help train a new generation of HQP, in Canada and beyond.