Quantum Physics research is conducted in the Quantum Measurement and Manipulation Group (QMMG) at Aarhus University with a theoretical and an experimental division. It's in the QMMG that the potential of producing and manipulating ultracold atoms is explored for a number of main goals.
In 2019, an unfortunate accident caused our experiment to catch fire. We had to dismantle, clean, and rebuild almost everything around the sensitive microscopy setup. As a result, we lost our single atom signals. However, on 9 June 2021, we were able to recover our single atom signal! Each of the pink dots in the image below represents one single rubidium-87 atom.
The brighter dots are in focus, the dimmer dots are out of focus. Check out our tomography work (see below, or the publications page) for more information on how we can determine where those out-of-focus atoms really are.
This is a huge step forward on our path for more excellent experimental science!
Check out our new paper on the preprint server: Spatial tomography of individual atoms in a quantum gas microscope, https://arxiv.org/abs/1912.03079.
We demonstrate a method to determine the position of single atoms in a three-dimensional optical lattice. Atoms are sparsely loaded from a far-off-resonant optical tweezer into a few vertical planes of a cubic optical lattice positioned near a high-resolution microscope objective. In a single realization of the experiment, we pin the atoms in deep lattices and then acquire multiple fluorescence images with single-site resolution. The objective is translated between images, bringing different vertical planes of the lattice into focus. In this way, we tomographically reconstruct the atom distribution in three dimensions. This opens up the possibility of extending the domain of quantum simulation using quantum gas microscopes from two to three dimensions.
Our paper, Spatially-selective in situ magnetometry of ultracold atomic clouds, is now published in Journal of Physics B. The paper can be found under the following link: iopscience.iop.org/article/10.1088/1361-6455/ab0bd6.
Our paper on the Alice Challenge and remote optimisation of BECs was finally published in PNAS.
We developed a versatile remote gaming interface that allowed external experts as well as hundreds of citizen scientists all over the world through multiplayer collaboration and in real time to optimize a quantum gas experiment in a lab at Aarhus University. Surprisingly, both teams quickly used the interface to dramatically improve upon the previous best solutions established after months of careful experimental optimization. Comparing domain experts, algorithms and citizen scientists is a first step towards unravelling how humans solve complex, natural science problems.
Check out our new paper on the preprint server: Spatially-selective magnetometry of ultracold atomic clouds, arxiv.org/abs/1811.01798.
We realise two types of high precision magnetometers, using Faraday imaging in a balanced homodyne setting. A novelty of the setup lies in the option to spatially shape the probe light, enabling local detection of one/selection of many atom clouds in a tweezer array. We also discuss how this setup could be used to enhance magnetic field sensitive quantum simulations in our quantum gas microscope experiment.
We are happy to announce that Carrie Ann Weidner will join the experimental team as a postdoctoral researcher for the next two years to come. Previously she did her PhD in the United States under the supervision of Dana Anderson, at JILA in Boulder, Colorado. There she built an atom interferometer in a system of shaken optical lattices. Welcome Carrie!
Our paper, Measurement-enhanced determination of BEC phase transitions, is now published in Journal of Physics B. The paper can be found under the following link: https://doi.org/10.1088/1361-6455/aad447.
Our PhD student Jens Schultz Laustsen defended his progress report, Method and systems needed for a Quantum gas microscope, with success. Nils Kjærgaard from the university of Otago, New Zealand came to be an external examiner. Congratulations to Jens, who will now continue working towards the ultimate goal of every PhD student.
With the latest progress in the lab on the high resolution imaging, we have been working on cleaning the signal to achieve better signal compared to the background level of noise. The image attached displays some tens of 87Rb atoms, trapped in deep optical lattices, and imaged by capturing fluorescent light emitted when the atoms are exposed to near resonant light.
As a result of past several months hard work, we have now achieved a greatly improved signal from single atoms trapped in the optical lattices. Here a heart shaped laser beam is projected into the atomic cloud yielding the atomic heart shape (as also reported on this page in an entry from 1 year ago, on the 31/5 2017). The difference is that now we can easily identify individual atoms, that ate the individual dots present in the image below. This is a big leap towards quality images from our quantum gas microscope.
This is also an opportunity to introduce a colormap for our quantum gas microscope. It goes through four colors, from black to purple to pink to white. Click on the image for an enlarged version.