Pieter W. Claeys



Quantum eigenstates from classical Gibbs distributions

22 January 2021

Our paper on Quantum eigenstates from classical Gibbs distributions has been published in SciPost Physics! Even better, it has been awarded the SciPost Select label, with inclusion of an extended abstract in SciPost Selections, "the highest mark of recognition given by the Editorial College". Various new results have been added to the published version compared to the preprint, including a numerical illustration of the Berry-Tabor and BGS conjectures in classical systems and extensive results for Hamiltonians including a vector potential, where we also found a way of obtaining Landau levels starting from the classical Gibbs distribution.

I'm pretty happy with how this paper has been received so far, including its inclusion in the Journal Club for Condensed Matter Physics. It also continues my positive experience with SciPost's model — where if you're interested, you can check out the paper's revision history here.

Quantum Chaos 2020

03 December 2020

With 2020 coming to an end, so is the Quantum Chaos 2020 seminar series. Pablo and I concluded this series by each giving a short talk about some of our research, with Pablo presenting on Quantifying the sensitivity to errors in noisy quantum simulators, whereas I discussed Thermalization and scrambling in dual-unitary circuit models . A massive thank you to all previous speakers and to everyone watching!

For anyone wanting to learn more about quantum chaos: all previous talks remain available to watch online here.

Shortcuts to Dynamic Polarization

13 November 2020

New work on the arXiv: check out our new paper on Shortcuts to Dynamic Polarization! We combine our recent work on the integrability of the central spin model with our approximate counterdiabatic protocols to speed up dynamical polarization in central spin models. Dynamical polarization protocols polarize a spin bath by repeatedly transfering polarization from the central spin to the surrounding spins. This polarization transfer tends to occur adiabatically, and we here show how this adiabatic transfer can be sped up by introducing additional control fields — which can be realized experimentally through Floquet protocols. We further use the integrable structure of the central spin to fully characterize the performance of all presented protocols, and show how we can reduce the necessary time scales by orders of magnitude. Great work from graduate student Tamiro Villazon in collaboration with Boston University's Anatoli Polkovnikov and Anushya Chandran.

Dynamic polarization protocols aim to hyperpolarize a spin bath by transferring spin polarization from a well-controlled qubit such as a quantum dot or a color defect. Building on techniques from shortcuts to adiabaticity, we design fast and efficient dynamic polarization protocols in central spin models that apply to dipolarly interacting systems. The protocols maximize the transfer of polarization via bright states at a nearby integrable point, exploit the integrability-breaking terms to reduce the statistical weight on dark states that do not transfer polarization, and realize experimentally accessible local counterdiabatic driving through Floquet-engineering. A master equation treatment suggests that the protocol duration scales linearly with the number of bath spins with a pre-factor that can be orders of magnitude smaller than that of unassisted protocols. This work opens new pathways to cool spin baths and extend qubit coherence times for applications in quantum information processing and metrology.