CAREER: Heat, Work and Information in Quantum Circuits

Washington University, Saint Louis MO

Investigators

Abstract

Thermodynamics is a field of physics which describes quantities such as heat and work and their relationship to entropy and temperature. Originally developed as a theory to optimize the efficiency of heat engines, two extensions of thermodynamics in the last century advanced the theory to the point at which quantum mechanics should be incorporated. First, the identification of the role of information in thermodynamics makes strong connections between heat, entropy and information. Second, extensions of thermodynamics to the realm of microscopic systems in which fluctuations are significant allow the application of thermodynamics at the level of single trajectories of classical particles. Quantum mechanics requires both of these features as information and fluctuations are central to the behavior of quantum systems. The experimental control over single quantum systems that has been achieved in this century places us in a unique position to extend thermodynamics into the quantum regime. Understanding quantum thermodynamics will be increasingly important as quantum machines become more complicated and as classical machines are further miniaturized. The experimental work will utilize microscopic superconducting circuits as artificial atoms and the interaction of these atoms with microwave light to control the atom's environment. The team will conduct a series of experiments elucidating the relationship between quantum information, heat and work. An additional goal of this project is to increase the diversity and talent pool of future physicists. The team will create a three and a half day pre-orientation program for entering freshman focused on building community among women and minority physics majors. The project builds on previous work using superconducting artificial atoms and the physics of cavity quantum electrodynamics to create quantum systems with exquisite control over the environment of the system. The team will undertake a series of experiments to study the relationship between quantum information and the thermodynamic quantities of heat and work. The first experiment will examine the interplay between quantum feedback, quantum coherence, and work in a continuously monitored superconducting qubit that realizes a quantum version of Maxwell's demon. The team will look for uniquely quantum features stemming from the quantum coherence of the qubit and the backaction of the continuous measurement. In the second project the team will create a single atom heat engine that utilizes the electronic degrees of freedom of a superconducting artificial atom. This will explore how quantum superposition, entanglement, and quantum control can affect the Carnot efficiency of the engine. In a final experiment, the team will study the microscopic physics of thermalization with a thermal bath from the perspective of quantum measurement by simultaneously monitoring heat transfer to and from the bath. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.