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Imaging Fermionic Atoms in a Quantum Gas Microscope

When cooled near absolute zero, a dilute gas of atoms behaves according to the rules of quantum mechanics. Due to the precise control with which these ultracold gases can be trapped and manipulated, they form an exemplary system in which to study many-body quantum physics. Using different species of atoms allows the study of bosonic or fermionic quantum particles, the interaction strength between particles can be tuned over a wide range, and many different magnetic and optical potentials are available.  Taking advantage of the range of tunable parameters, experiments with ultracold gases can be used as quantum simulators to study the behaviour a particular many-particle Hamiltonian.

To simulate the physics of electrons in the crystal lattice of a material, ultracold atoms can be placed in an optical lattice – a periodic potential generated by the interference of several laser beams. Experiments with optical lattices have been used to explore the quantum phase transition of a Bose gas between superfluid and Mott insulating states, the effect of strong interparticle interactions in graphene, and the response of particles to extremely strong applied magnetic field. To precisely read out the results of these kinds of simulations, experiments using bosonic rubidium atoms have incorporated high-resolution fluorescence imaging of atoms trapped in the optical lattice, allowing for a measurement of the density correlations at the level of single atoms and single lattice sites. Experiments which read out the results of a lattice quantum simulation with single-site precision have been termed ‘quantum gas microscopes’.

Recently, our lab has finished construction of a new quantum gas microscope experiment which extends the capability for single-atom and single-site resolved imaging to a fermionic species of atom. This development opens many new avenues for quantum simulation, including an investigation of the antiferromagnetic states of the Hubbard model which may be linked to the ‘high-Tc’ superconductivity of cuprate materials. In this talk I will outline the challenge of achieving single-atom sensitive fluorescence imaging and outline the details of our experiment which achieves quantum gas microscopy with fermionic 40K.