PQI/ Condensed Matter Seminar: Kater Murch (Washington University- St. Louis

November 2, 2017 - 4:00pm to 5:00pm
Title: Quantum Thermodynamics with Superconducting Qubits
Abstract: The laws of thermodynamics are fundamental laws of nature that classify energy changes for macroscopic systems as work performed by external
driving and heat exchanged with the environment. In the past decades, these principles have been successfully extended to the level of
classical trajectories of microscopic systems to account for thermal fluctuations. In particular, experimentally tested generalizations of
the second law, known as fluctuation theorems, quantify the occurrence of negative entropy production. The extension of thermodynamics to
include quantum fluctuations faces unique challenges such as the proper identification of heat and work and clarification of the role of quantum
coherence. I will present experiments that allow us to track heat and work along single quantum trajectories of a superconducting qubit
evolving under continuous unitary evolution and measurement. We are able to verify the first law of thermodynamics in that the measured heat and
work sum to the total energy change of the quantum system. We then verify the second law of thermodynamics in the form of the Jarzynski
equality by employing a novel quantum feedback loop that cancels the heat exchanged at each point in time with additional work. Our
results successfully generalize stochastic thermodynamics to the quantum regime, paving the way for future experimental and theoretical
investigations of quantum information and thermodynamics.

Location and Address

321 Allen Hall