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A quantum gas microscope for fermions

Until recently, imaging of individual atoms in a quantum gas microscope had only been achieved for bosonic species. EU-funded researchers have for the first time captured fluorescence images of ultracold fermionic potassium atoms.
A quantum gas microscope for fermions
Electrons, protons, neutrons and even quarks are all fermions – in other words, particles with half-integer spin. Unlike bosons with integer spin, fermions cannot occupy the same quantum state. This simple fact leads to the structure of elements where electrons have to occupy different orbits around the atomic nucleus.

When fermions interact with each other, they form atomic nuclei and solid-state materials. Their collective behaviour also gives rise to exotic phenomena like high-temperature superconductivity and colossal magnetoresistance. Still, current understanding of strongly interacting systems of fermions is limited.

For researchers working on the EU-funded project FERMISITE (Strongly correlated fermions in optical lattices with single-site resolution), ultracold atomic fermionic gases offered a pristine platform to study many-body solid-state physics. Particularly, fermionic atoms trapped in an optical lattice simulate the physics of electrons in a crystalline solid.

In their experiment, the researchers utilised such an optical lattice formed by retro-reflected laser beams. To resolve atoms with single-lattice-site resolution, they devised a new set-up that incorporates a vertical beam retro-reflected at the coated vacuum window.

Potassium-40 atoms were prepared by laser cooling and forced evaporation at the focal plane of this magneto-optical trap. Fluorescence imaging was then performed to detect the atoms while the atoms were cooled. To make the potassium atoms fluorescent, they were illuminated by off-resonant light.

Similar experiments were conducted around the same time by researchers at Harvard University and the Massachusetts Institute of Technology (MIT) in the United States and at the Max-Planck Institute for Quantum Optics in Garching, Germany. The advent of fermion gas microscopy opens the way for the study of many-fermion systems trapped in optical lattices.

The study of such quantum systems in well-controlled engineering environments will shed light on the behaviour of other fermions. In particular, a quantum simulation of fermions with single-particle resolution will be an excellent test bed to investigate properties of strongly correlated quantum systems that are difficult to resolve with numerical simulation methods.

Related information


Quantum gas microscope, fermions, potassium atoms, atomic nuclei, FERMISITE, optical lattice
Record Number: 182689 / Last updated on: 2016-05-18
Domain: Industrial Technologies
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