Pieter W. Claeys



Counterdiabatic driving, adiabatic gauge potentials, and Floquet-engineering

09 April 2019

Publication news - our preprint about counterdiabatic driving in quantum many-body systems has appeared on arXiv! A new topic for me, albeit with some interesting connections with my Ph.D. research. Joint work with Mohit Pandey, Dries Sels, and Anatoli Polkovnikov.

When changing a system from state A to state B, this is usually done extremely slow (adiabatically), carefully attempting not to disturb the system. However, in practice we can't take arbitrarily long due to system constraints, external noise,... One interesting way of speeding up such processes is through counterdiabatic driving, where we explicitly counteract the forces arising when changing a system a finite rate. However, it is generally extremely hard to (a) know what forces to apply and (b) know how to realize these forces. Mathematically, everything is encoded in the adiabatic gauge potential, and in this preprint we show how this potential can be approximated in a surprisingly accurate way and how the resulting forces and counterdiabatic driving can be realized through a 'simple' shaking of the system.

Floquet-engineering counterdiabatic protocols in quantum many-body systems: Counterdiabatic (CD) driving presents a way of generating adiabatic dynamics at arbitrary pace, where excitations due to non-adiabaticity are exactly compensated by adding an auxiliary driving term to the Hamiltonian. While this CD term is theoretically known and given by the adiabatic gauge potential, obtaining and implementing this potential in many-body systems is a formidable task, requiring knowledge of the spectral properties of the instantaneous Hamiltonians and control of highly nonlocal multibody interactions. We show how an approximate gauge potential can be systematically built up as a series of nested commutators, remaining well-defined in the thermodynamic limit. Furthermore, the resulting CD driving protocols can be realized up to arbitrary order without leaving the available control space using tools from periodically-driven (Floquet) systems. This is illustrated on few- and many-body quantum systems, where the resulting Floquet protocols significantly suppress dissipation and provide a drastic increase in fidelity.

Lindau Nobel Laureate Meeting

18 March 2019

Excellent news and something I'm already looking forward to: I have been selected to participate in the 69th Lindau Nobel Laureate Meeting! From 31 June to 5 July I will be joining almost 600 other young scientists in Lindau, Germany, to discuss physics and attend lectures, discussion sessions and masterclasses with over 40 Nobel Laureates in Physics and related fields. This selection followed an initial selection and nomination by the Research Foundation Flanders (FWO Vlaanderen), whose funding is gratefully acknowledged.

Once every year, more than 30 Nobel Laureates convene in Lindau to meet the next generation of leading scientists: 500-600 undergraduates, PhD students, and post-doc researchers from all over the world. The Lindau Nobel Laureate Meetings foster the exchange among scientists of different generations, cultures, and disciplines.

APS March Meeting

04 March 2019

Tomorrow I will be presenting our work on Floquet resonances in the central spin model in the APS March Meeting currently taking place in Boston, during the session Non-Equilibrium Physics in AMO Systems II. According to the abstract:

Adiabatically varying the driving frequency of a periodically driven many-body quantum system can induce controlled transitions between resonant eigenstates of the time-averaged Hamiltonian, corresponding to adiabatic transitions in the Floquet spectrum and presenting a general tool in quantum many-body control. Using the central spin model as an application, we show how such controlled driving processes can lead to a polarization-based decoupling of the central spin from its decoherence-inducing environment at resonance. While it is generally impossible to obtain the exact Floquet Hamiltonian in driven interacting systems, we exploit the integrability of the central spin model to show how techniques from quantum quenches can be used to explicitly construct the Floquet Hamiltonian in a restricted many-body basis and model Floquet resonances..