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UID:69d4c4f7dff01
DTSTART:20241122T090000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:Auditorium
SUMMARY:ICFO | SANDRA BUOB
CLASS:PUBLIC
DESCRIPTION:Ultracold atoms have proven to be a valuable asset to study and
  understand complex quantum many-body systems in a well-controlled setting
 . In particular\, quantum-gas microscopes provide unprecedented access to 
 local observables and allow one to investigate those systems at the level 
 of each individual particle\, giving new insights on their behaviour. Whil
 e so far most of these microscopes used alkali atoms\, the distinct proper
 ties of alkaline-earth atoms\, in particular strontium\, combined with qua
 ntum-gas microscopy are expected to shed new light on a broad variety of m
 any-body problems. This thesis describes the realization of single-site-re
 solved imaging for both bosonic and fermionic strontium atoms in a Hubbard
 -regime optical lattice\, which unlocks the possibility to study novel typ
 es of Bose- and SU(N) Fermi-Hubbard systems.\nAn essential step in ultraco
 ld-atom experiments is the preparation of a quantum degenerate cloud. In t
 he first part of this thesis\, we discuss the methods we have implemented 
 in our apparatus to achieve this goal. We developed a new resonant-shieldi
 ng method to double the atom number during the first cooling stage in a br
 oad-linewidth blue magneto-optical trap. During the second cooling stage i
 n a narrow-linewidth red magneto-optical trap\, the hyperfine structure of
  the fermionic atoms adds additional challenges which are addressed by mix
 ing the hyperfine states with an additional laser for efficient trapping a
 nd cooling. After the laser-cooling stages\, we perform evaporative coolin
 g in a far red-detuned optical potential before loading the atoms into a t
 wo-dimensional optical lattice. The lattice laser operates at the clock-ma
 gic wavelength of strontium (813.4nm) which will enable high-precision mea
 surements in future experiments.\nTo image the individual atoms in the opt
 ical lattice\, we place a high-NA objective in close vicinity to the atoms
 . We demonstrate single-atom resolution for bosonic and fermionic strontiu
 m and successfully reconstruct the lattice occupation for both of them\, r
 eaching fidelities as high as 96%. For the bosonic Sr-84 atoms\, we induce
  fluorescence on the blue broad-linewidth transition and simultaneously pe
 rform attractive Sisyphus cooling on the red narrow-linewidth transition. 
 Moreover\, combining this imaging method with momentum-space detection\, w
 e observe the matter-wave interference arising from the phase coherence of
  the Bose-Hubbard superfluid. For the fermionic Sr-87 atoms\, we image wit
 h the red transition only\, which allows us to obtain for the first time f
 or a fermionic alkaline-earth atom both single-atom resolution and spin-re
 solved detection.\nThis thesis has combined\, for the first time\, quantum
 -gas microscopy with ultracold strontium and its distinct spectral propert
 ies. This platform should enable a broad range of future studies. For the 
 bosons\, it unlocks investigation of the single-atom-resolved dissipative 
 Bose-Hubbard systems and the exploration of collective atom-photon scatter
 ing in ordered atomic arrays. For the fermions\, the spin-dependent single
 -atom detection provides the ideal setting for investigations of antiferro
 magnetic correlations in SU(N&le\;10) Fermi-Hubbard systems and the realiz
 ation of exotic magnetic phases.\n&nbsp\;\nFriday November 22\, 10:00 h. I
 CFO Auditorium \nThesis Director: Prof. Dr. Leticia Tarruell
DTSTAMP:20260407T084855Z
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