Physics (Internal)

Universal High-Frequency Limits of Periodically Driven Systems: from Classical Dynamical Stabilization to Quantum Floquet Engineering

This event is part of the Preliminary Oral Exam.

Examining Committee: Anatoli Polkovnikov,Claudio Chamon, Ami Katz, Shyam Erramilli

Abstract:

Periodically driven systems are currently experiencing an unprecedented flurry of interest. Proposed theoretically, and successfully verified experimentally, nonequilibrium models have been invented in which, by means of an ultra-fast periodic drive, the properties of a system can be changed drastically. For instance, periodic driving is found to turn unstable equilibria into stable ones; neutral atoms can be re-designed to 'feel' magnetic fields much stronger than what current magnets can produce today; topologically-trivial systems are cast into topological insulators which exhibit robust edge states suitable for quantum computing.

Starting from Floquet theory, I will discuss the underlying theoretical ideas behind some of these models, giving a classification of different driving scenarios that can be employed to achieve optimal engineering results. I will then present a universal method to obtain the effective high-frequency Hamiltonian, illustrated on several examples. Finally, I will elaborate on different possibilities of performing measurements in these systems, and introduce the concept of 'Floquet measurements', which are not only of high experimental interest, but have the potential to reveal the physics of the high-frequency effective Hamiltonian as well.