Researchers from the Institute of Laser Physics at Universität Hamburg have
developed a new technique for quantum gas microscopy that now allows imaging
of three-dimensional quantum systems. In the journal Nature, they report on
the new method, which can be used to explore entirely new regimes.
In quantum simulation, researchers study a controlled quantum system in the
laboratory to understand the physics of another, less controlled system. For
example, one uses ultracold atoms trapped in standing waves of laser light
to mimic the physics of electrons in solid-state materials and gain new
insights into their quantum phases. In addition to the controlled
preparation of the system, imaging is also crucial. For example, quantum gas
microscopes allow the detection of all particles in the quantum system and
thus give access to arbitrary correlation functions to characterize the
state. This technology is based on the optical resolution of the lattice
sites at intervals of typically half a micrometer and was therefore
previously limited by depth of field to two-dimensional systems.
Magnification through matter wave optics
In the new method developed by the Hamburg researchers led by Dr. Christof
Weitenberg and Prof. Klaus Sengstock, both of whom also conduct research in
the Cluster of Excellence "CUI: Advanced Imaging of Matter", this is now
overcome, and the resolution of three-dimensional systems is also possible.
For this purpose, the scientists use so-called matter wave optics, i.e., a
magnification of the density distribution of the ultracold atoms themselves
by a factor of up to 90. The optical imaging of the atoms after this
magnification is then simply possible without limitation of diffraction or
depth of field. Matter-wave optics is based on a lens in the form of a
harmonic trap, which is turned on for a quarter period, and a subsequent
free expansion of the atoms. Both processes lead to a transformation between
real space and momentum space and, in combination, to the magnifying image.
The researchers use the new technique to study Bose-Einstein condensates of
ultracold rubidium atoms in an optical lattice. In this way, they can make a
particularly precise measurement of the phase transition into the
Bose-Einstein condensate. Next, the researchers want to further develop the
new microscopy technique. This should make it possible to detect all atoms
individually in a regime of just a few atoms per lattice site. In addition,
by modifying the matter-wave optics, it will be possible to measure not only
the density but also the coherence properties of the system in a spatially
resolved manner. Luca Asteria, who developed the technique with his
colleagues, explains, "With this microscopy technique, we can explore
completely new regimes that were not accessible before."
Reference:
Asteria, L., Zahn, H.P., Kosch, M.N. et al. Quantum gas magnifier for
sub-lattice-resolved imaging of 3D quantum systems. Nature 599, 571–575
(2021).
DOI: 10.1038/s41586-021-04011-2
Tags:
Physics