Spin-resolved single-atom microscopy of 87Sr

Abstract

Quantum simulations with ultracold atoms are a powerful and versatile tool for investigating models of complex quantum materials that are intractable with classical computational methods. Simulating the Fermi-Hubbard model with atomic quantum simulators is of particular relevance since it is expected to provide fundamental insights into correlated quantum systems and facilitate the development of advanced quantum technologies. Despite substantial progress in controlling and probing such systems, experimental challenges persist. In particular, quantum simulations of the SU(N) Fermi-Hubbard model require challenging imaging techniques with state and single-atom resolution of atoms with multiple spin states. In this thesis, we present a novel experimental approach employing optical Stern-Gerlach potentials to spatially separate and detect multiple nuclear spin states in fermionic strontium atoms. Our setup utilizes a combination of vacuum, magnetic field, and laser systems to produce ultracold bosonic and fermionic strontium samples at sub-μK temperatures. Subsequently, single atoms are prepared with higher than 99% fidelity in a tweezer trap. After releasing the atom from the tweezer, a precisely positioned tensor potential is applied to the atom. The tensor potential depends on the absolute value of the ground state spin state |mF| and creates a spin-dependent, Stern-Gerlach-like force that spatially separates the atoms based on their initial spin state. After a free-expansion time, we rapidly image the atom in free space with fluorescence imaging beams and obtain a detection fidelity of 98%. This technique enables the simultaneous detection of up to four nuclear spin states with fidelities between 93.6% and 99.7%. Furthermore, we demonstrate the capability to monitor coherent nuclear spin dynamics following a magnetic-field quench, highlighting the potential of these systems for quantum information processing. The developed imaging technique opens new avenues for quantum simulations with multi-electron atoms and the realization of the SU(N) Fermi-Hubbard model, thus offering promising perspectives for exploring strongly correlated quantum phenomena and advancing quantum technologies.