CsLat | UMQT

Research Associate studying quantum gases in complex lattices

Sun, 20 Apr 2025 00:00:00 +0000

We have an open postdoctoral position as part of the newly starting EPSRC Programme Grant, Quantum Advantage in Quantitative Quantum Simulation (QQQS). The project focuses on the study of quantum many-body states of ultracold gases in periodic potentials. Please check our recent projects to learn more about our research and the team.

Interested in joining us?
Contact us now for further details!

Start date: Any
Requirements: PhD in Experimental Physics
Contact: Dr Elmar Haller

Experimental Observation of Single- and Multi-Site Matter-Wave Solitons in 1D Optical Lattices

Wed, 01 Jan 2025 00:00:00 +0000

Caesium in lattice potentials

Sat, 01 Jan 2022 00:00:00 +0000

Floquet Solitons and Dynamics of Periodically Driven Matter Waves with Negative Effective Mass

Wed, 01 Dec 2021 00:00:00 +0000

Floquet solitons of matter waves

Sun, 01 Aug 2021 00:00:00 +0000

Abstract

We experimentally study the dynamics of a weakly interacting Bose-Einstein condensate of cesium atoms in a 1D optical lattice with a periodic driving force. After a sudden start of the driving we observe the formation of stable wave packets at the center of the fi rst Brillouin zone (BZ) in momentum space, and we interpret these as Floquet solitons in periodically driven systems. The wave packets become unstable when we add a trapping potential along the lattice direction leading to a redistribution of atoms within the BZ.

The concept of a negative effective mass and the resulting changes to the interaction strength and effective trapping potential are used to explain the stability and the time evolution of the wave packets. We expect that similar states of matter waves exist for discrete breathers and other types of lattice solitons in periodically driven systems. Phys. Rev. Lett. 127, 243603 (2021).

We further demonstrated non-destructive readout using state-selective imaging on the stretched state transition to enable post-selection for loss and avoiding the requirement to reload the arrays after every sequence.

For more details see our publication arXiv:2301.10510 (2023)."

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Good internal reference of author Dr. A. La Rooij

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Matter waves with position-dependent interactions

Wed, 28 Oct 2020 00:00:00 +0000

Motivation

Atoms can show attractive or repulsive interactions when they collide. But can atoms be both attractive and repulsive at the same time, e.g. attractive on the left side and repulsive on the right side?

The answer is: yes they can. The wave function of an ultracold atoms can be very large, extending over 100s of micrometers. We are used to the fact that the wave function adapts locally to a varying potential energy over this distance. Surprisingly, the same is true for its scattering properties, which can also vary locally over the extend of the wave function. The concept of an atom with locally changing interactions is only counterintuitive when we think of atoms as point like objects that crash into each other. A description using matter waves with fluid-like properties is well-suited to analyze those so called ‘‘collisionally inhomogeneous’’ systems.

Project summary

Collisionally inhomogeneous fluids exhibit spatially varying interactions between their particles. They frequently occur at interfaces, where interaction properties change due to a variation of an external potential or due to a change of the fluid’s composition. Examples for fluids at interfaces with a collisional inhomogeneity are liquid-vapour surfaces, and material junctions in condensed-matter physics.

We studied the evolution of matter waves for the simplest case, i.e. a spatial gradient of the interaction strength. Starting with a Bose-Einstein condensate with weak repulsive interactions in quasi-one-dimensional geometry, we monitored the evolution of a matter wave that simultaneously extends into spatial regions with attractive and repulsive interactions. We observed the formation and the decay of soliton-like density peaks, counter-propagating self-interfering wave packets, and the creation of cascades of solitons.

The matter-wave dynamics was well reproduced in numerical simulations based on the non-polynomial Schroedinger equation with three-body loss, allowing us to better understand the underlying behavior based on a wavelet transformation [Phys. Rev. Lett. 125, 183602 (2020)].

Collisionally inhomogeneous Bose-Einstein condensates with a linear interaction gradient

Thu, 01 Oct 2020 00:00:00 +0000

Interferometric measurement of micro-g acceleration with levitated atoms

Wed, 01 May 2019 00:00:00 +0000