Abstract:
Simulating highly correlated quantum systems with classical computers exceed their capa-
bilities as the system size increases. In analog quantum simulators, the system of interest
is mimicked by another quantum system in a highly controllable and accessible environ-
ment. Even though quantum simulations with ultracold atoms have been demonstrated
successfully, ultra-low temperature regimes are experimentally challenging to achieve and
still remain to be explored. New approaches to realizing ever lower temperatures, especially
in Fermi systems, have been and continue to be a constant pursuit in Atomic, Molecular,
and Optical Physics (AMO).
Within this thesis, a new quantum gas experiment of fermionic
6Li and bosonic 166Er is
presented and first results on sympathetic cooling of Li to quantum degeneracy by Er are
demonstrated. The experimental apparatus is described in detail with a focus on the Li
subsystem of the dual-species experiment. Standard and further developed laser cooling
techniques used to produce a Magneto-Optical Trap (MOT) of Li are characterized, along
with their associated vacuum system stages. In this context, a combined Optical Pumping
/ Transversal Cooling (OP/TC) technique of the atomic beam on the D1-line is presented,
and an enhancement of the MOT loading rate by one order of magnitude is demonstrated.
The architecture and building blocks of the laser system for providing resonant light at
671 nm for laser cooling of Li are detailed, and laser locking techniques for frequency
stabilization and light amplification by injection locking of high-power laser diodes are
presented. Special focus is placed on the introduction and characterization of a new laser-
diode-independent injection locking technique, keeping spectrally pure amplified light by a
periodic slave current optimization routine executed by a microcontroller. The system has
been submitted for patent approval.
In further steps of optical cooling of Li, a non-standard free-space Gray Molasses (GM)
technique based on intensity ramps, providing temperatures as low as 13 µK, is presented.
The non-standard technique is characterized and compared to the standard pulse GM
approach, which typically achieves 50 µK only. Cooling steps for preparing an ultracold Li
cloud in the glass cell start from an Optical Dipole Trap (ODT) loaded by a compressed
Magneto-Optical Trap (cMOT) and consecutive evaporation into a 1D transport lattice of
counter propagating 1064 nm laser beams. By detuning one of the lattice beams, optical
transport over 1 m to the glass cell with an efficiency of 74% is demonstrated.
In a combined ErLi sequence, the two species are transported to the glass cell together
and loaded to 1064 nm ODTs. Sympathetic cooling of Li by forced evaporation of Er to
T/TF = 0.77 ± 0.10 next to the production of an Er BEC are presented.
To conclude, this work introduces a new promising dual-species quantum gas experiment
and its ability for providing sympathetic cooling of Li by Er to quantum degeneracy is demon-
strated. These findings are an encouraging foundation for achieving higher degeneracies by
refined experimental control in pursuit of penetrating unexplored temperature regimes in
quantum simulators.
Fermi-Bose mixture