Quantum gas microscopy provides an exciting platform for the study of in situ atom-atom interactions. Recent advances in quantum gas microscopy have allowed the probing of the Bose-Hubbard and Fermi-Hubbard Hamiltonian with a variety of atomic species. In this thesis, we are currently extending these platforms with the introduction of an Erbium Dipolar Quantum Gas Microscope which will allow us to study dipole-dipole interactions in a lattice. Erbium has several exciting properties, which increase the control and flexibility of these systems. These include stable bosonic and fermionic isotopes, a large magnetic dipole moment (7uB), a large spin value (J=6 and F=19/2 for bosonic and fermionic isotopes), a rich Feshbach spectrum, and several useful broad and narrow atomic transitions. A broad 401 nm transition can be used for imaging, which in combination with a 266 nm lattice spacing will provide fast time scales and access to a dipole-dipole interaction of approximately 30 Hz. This thesis will document the progress toward an Erbium Quantum Gas Microscope and include a variety of systems which have been developed. It will also show the first ever 841nm, red-detuned Magneto-Optical Trap with temperatures as low as 400 nK and a phase space density up to 0.05. This, in combination with other improvements, will allow for faster cycle times and more control over the system. These developments will allow us to benefit from the long-range interaction of Erbium and probe the Extended Bose-Hubbard and Extended Fermi-Hubbard Hamiltonian to an unprecedented degree.
Quantum gas microscopy provides an exciting platform for the study of in situ atom-atom interactions. Recent advances in quantum gas microscopy have allowed the probing of the Bose-Hubbard and Fermi-Hubbard Hamiltonian with a variety of atomic species. In this thesis, we are currently extending these platforms with the introduction of an Erbium Dipolar Quantum Gas Microscope which will allow us to study dipole-dipole interactions in a lattice. Erbium has several exciting properties, which increase the control and flexibility of these systems. These include stable bosonic and fermionic isotopes, a large magnetic dipole moment (7uB), a large spin value (J=6 and F=19/2 for bosonic and fermionic isotopes), a rich Feshbach spectrum, and several useful broad and narrow atomic transitions. A broad 401 nm transition can be used for imaging, which in combination with a 266 nm lattice spacing will provide fast time scales and access to a dipole-dipole interaction of approximately 30 Hz. This thesis will document the progress toward an Erbium Quantum Gas Microscope and include a variety of systems which have been developed. It will also show the first ever 841nm, red-detuned Magneto-Optical Trap with temperatures as low as 400 nK and a phase space density up to 0.05. This, in combination with other improvements, will allow for faster cycle times and more control over the system. These developments will allow us to benefit from the long-range interaction of Erbium and probe the Extended Bose-Hubbard and Extended Fermi-Hubbard Hamiltonian to an unprecedented degree.
Quantum gas microscopy of dipolar atoms is a promising opportunity to expand upon previous quantum simulations of neutral atoms in optical lattices. Erbium atoms interact via the long-range magnetic dipole-dipole interaction, which leads to a variety of new many-body effects and strongly correlated phases that are currently unexplored in microscopes with only short-range interactions. In this thesis I will detail progress toward the construction of an erbium quantum gas microscope as well as the techniques we implemented to produce a Bose-Einstein condensate of 8×104 atoms in under a second. These include the installation of a dual-stage magneto-optical trap, a stroboscopic optical dipole trap, as well as a tunable crossed optical dipole trap that allows for efficient evaporation of both bosonic and fermionic isotopes. I will also discuss the frequency stabilization systems we have implemented to produce laser linewidths of less than 1 kHz for near-resonant laser cooling on narrow transitions and a custom, high NA reflective objective to be used as part of a high resolution imaging system. Finally, I will discuss the noise properties of charge-coupled devices and the photon counting techniques that are needed for having high fidelities while using fast imaging schemes.
Quantum gas microscopy is an exciting platform for the study ofin situatom-atom interactions.Erbium, a dipolar atom, presents an opportunity to extend previous quantum gas microscopy ex-periments to more complex systems influenced by long-range, anisotropic interactions. In this the-sis, I present progress towards a quantum gas microscope of erbium atoms, including details on thedesign of a novel accordion lattice system. This system will allow us to dynamically tune the spac-ing of both the vertical and horizontal optical lattices confining the atoms. In addition, I present onthe sub-second generation of erbium Bose-Einstein condensates, made possible by implementing atwo-stage magneto-optical trap and a crossed optical dipole trap with a tunable geometry.
Recent advances in using microscopes in ultracold atom experiment have allowed experimenters for the first time to directly observe and manipulate individual atoms in individual lattice sites. This technique enhances our capability to simulate strongly correlated systems such as Mott insulator and high temperature superconductivity. Currently, all ultracold atom experiments with high resolution imaging capability use bosonic atoms. In this thesis, I present our progress towards creating the fermionic version of the microscope experiment which is more suitable for simulating real condensed matter systems. Lithium is ideal due to the existence of both fermionic and bosonic isotopes, its light mass, which means faster experiment time scales that suppresses many sources of technical noise, and also due to the existence of a broad Feshbach resonance, which can be used to tune the inter-particle interaction strength over a wide range from attractive, non-interacting, and repulsive interactions. A high numerical aperture objective will be used to image and manipulate the atoms with single lattice site resolution. This setup should allow us to implement the Hubbard hamiltonian which could describe interesting quantum phases such as antiferromagnetism, d-wave superfluidity, and high temperature superconductivity. I will also discuss the feasibility of the Raman sideband cooling method for cooling the atoms during the imaging process. We have also developed a new electronic control system to control the sequence of the experiment. This electronic system is very scalable in order to keep up with the increasing complexity of atomic physics experiments. Furthermore, the system is also designed to be more precise in order to keep up with the faster time scale of lithium experiment.
The development of quantum-gas microscopes has brought novel ways of probing quantum degenerate many-body systems at the single-atom level. Until now, most of these setups have focused on alkali atoms. Expanding quantum-gas microscopy to alkaline-earth elements will provide new tools, such as SU( N )-symmetric fermionic isotopes or ultranarrow optical transitions, to the field of quantum simulation. Here we demonstrate the site-resolved imaging of a 84 Sr bosonic quantum gas in a Hubbard-regime optical lattice. The quantum gas is confined by a two-dimensional in-plane lattice and a light-sheet potential, which operate at the strontium clock-magic wavelength of 813.4 nm. We realize fluorescence imaging using the broad 461-nm transition, which provides high spatial resolution. Simultaneously, we perform attractive Sisyphus cooling with the narrow 689-nm intercombination line. We reconstruct the atomic occupation from the fluorescence images, obtaining imaging fidelities above 94 % . Finally, we realize a 84 Sr superfluid in the Bose-Hubbard regime. We observe its interference pattern upon expansion, a probe of phase coherence, with single-atom resolution. Our strontium quantum-gas microscope provides a new platform to study dissipative Hubbard models, quantum optics in atomic arrays, and SU( N ) fermions at the microscopic level. Published by the American Physical Society 2024
Long-range interactions are important to complex physical systems. Specifically in quantum mechanical many-body systems, long-range interactions promote spatial structures, give rise to quantum frustration, and generate quantum entanglement. Nevertheless, quantum simulations of lattice systems have largely not been able to realize long-range interactions. Many efforts are underway to explore long-range interacting lattice systems using polar molecules, Rydberg atoms, and magnetic atoms. In this thesis, I present the realization of long-range interacting itinerant systems using magnetic erbium atoms. I start by discussing the construction of the Erbium quantum gas microscope, including the installation of an in-vacuum high-numerical-aperture objective, various optical lattices, and potential projection through the objective. Then, I present emerging quantum phases with half-filling and directly probe the spatial structures of dipolar quantum solids using site-resolved imaging. A kaleidoscope of phases emerges as we tune the dipolar interaction, demonstrating the great tunability of this experimental platform. The dipolar interactions can be tuned slowly to study first-order quantum phase transitions between different solids. Next, I discuss topological phases that emerge with unity filling. With a zoo of Fano-Feshbach resonances, erbium atoms are gifted with the flexibility of widely tunable on-site interaction, allowing continuous probing of the quantum phase transitions between topologically trivial and non-trivial phases. We explore average symmetry protected topological phases as an instance of the mixed state quantum order. Finally, I briefly discuss the observation of spin squeezing with itinerant systems and super- and sub-radiance in a sub-wavelength optical lattice.
Since the achievement of quantum degeneracy in gases of chromium atoms in 2004, the experimental investigation of ultracold gases made of highly magnetic atoms has blossomed. The field has yielded the observation of many unprecedented phenomena, in particular those in which long-range and anisotropic dipole-dipole interactions (DDIs) play a crucial role. In this review, we aim to present the aspects of the magnetic quantum-gas platform that make it unique for exploring ultracold and quantum physics as well as to give a thorough overview of experimental achievements. Highly magnetic atoms distinguish themselves by the fact that their electronic ground-state configuration possesses a large electronic total angular momentum. This results in a large magnetic moment and a rich electronic transition spectrum. Such transitions are useful for cooling, trapping, and manipulating these atoms. The complex atomic structure and large dipolar moments of these atoms also lead to a dense spectrum of resonances in their two-body scattering behaviour. These resonances can be used to control the interatomic interactions and, in particular, the relative importance of contact over dipolar interactions. These features provide exquisite control knobs for exploring the few- and many-body physics of dipolar quantum gases. The study of dipolar effects in magnetic quantum gases has covered various few-body phenomena that are based on elastic and inelastic anisotropic scattering. Various many-body effects have also been demonstrated. These affect both the shape, stability, dynamics, and excitations of fully polarised repulsive Bose or Fermi gases. Beyond the mean-field instability, strong dipolar interactions competing with slightly weaker contact interactions between magnetic bosons yield new quantum-stabilised states, among which are self-bound droplets, droplet assemblies, and supersolids. Dipolar interactions also deeply affect the physics of atomic gases with an internal degree of freedom as these interactions intrinsically couple spin and atomic motion. Finally, long-range dipolar interactions can stabilise strongly correlated excited states of 1D gases and also impact the physics of lattice-confined systems, both at the spin-polarised level (Hubbard models with off-site interactions) and at the spinful level (XYZ models). In the present manuscript, we aim to provide an extensive overview of the various related experimental achievements up to the present.