Magic Wavelengths and
Dipole-Dipole Interactions in
Ultracold RbCs Molecules

Abstract

Ultracold polar molecules have become the subject of burgeoning fields
of research in recent years owing to their prospects in quantum simulation,
quantum computation and precision measurement. Their relatively large
ground state dipole moment, coupled with a complex internal structure forms
an incredibly powerful toolbox in which to perform quantum science experiments. Unfortunately, spatial confinement using light, which is necessary for
many of the aforementioned applications, causes differential ac Stark shifts
between quantum states, limiting coherence times and stifling their applicability. By accessing a so-called magic condition, this effect can be eliminated.
This thesis presents work towards producing a quantum simulator based
on a bulk gas of 87Rb133Cs molecules. We develop a magic wavelength trap
by exploring nominally forbidden transitions from the X1Σ
+ ground state to
b
3Π0 states. By tuning our trapping laser between transitions to different
vibrational states of b3Π0, we can arbitrarily tune the difference in polarisability between pairs of rotational states and engineer second-scale coherence
times. When we trap our molecules in a superposition of rotational states
that exhibit a dipole moment in the laboratory frame, we observe the effects
of long-range dipole-dipole interactions between molecules. These dipole-dipole interactions form the basis for quantum simulation and computation
applications, observations of which marks an important milestone for realising a quantum simulator using 87Rb133Cs. We then demonstrate a route to
ground state 87Rb133Cs molecules that is compatible with a protocol for loading Feshbach molecules into an optical lattice, developed by researchers at the
University of Innsbruck. This method can be combined with a magic wavelength trap to produce a sample of 87Rb133Cs molecules in a magic lattice.
Finally, we engineer synthetic dimensions that simulate simple single-particle
Hamiltonians by coupling multiple rotational states in 87Rb133Cs. This forms
the foundations for utilising rotational states of diatomic molecules as a platform for exploring synthetic dimensions