Characterizing Few-Fermion Systems with Momentum Correlations

@article{JanPhD,
  title = {Characterizing Few-Fermion Systems with Momentum Correlations},
  author = {Becher, Jan},
  journal = {PhD Thesis},
  year = {2020},
  month = {May},
  abstract = {In this thesis I report on the experimental study of fermionic systems in two complementary
experimental settings, i.e. large ensembles of dipolar erbium atoms and
few-particle systems of fermionic lithium trapped in optical tweezers.
Compared to alkali atoms, dipolar quantum gases offer new avenues to explore due
to their long-range anisotropic interactions and a rich internal structure. Such richness
comes at the cost of complexity and therefore requires precise investigations of
the atomic properties as well as the development of new experimental methods. In
the first part of this thesis we present measurements of the anisotropic light shift
of erbium atoms and compare the results to semiempirical electronic-structure calculations.
Measurements of scalar and tensor polarizabilies of the ground and one
excited state show good agreement with calculated values. We furthermore present
the first experimental realization of a two-component strongly-interacting Fermi gas
with dipolar interactions. We identify several intra and interspin Feshbach resonances
at low magnetic field and precisely map out the scattering length across one broad
resonance.
The second part of this thesis is dedicated to the characterization of small fermionic
systems with momentum correlation measurements. Starting with systems of two or
three indistinguishable fermions, we detect and discuss second and third-order momentum
correlations that arise from quantum statistics alone. We then extend the
study of correlation functions to interacting systems and develop a scheme to constrain
large parts of the density matrix. Based on these constraints we reconstruct physical
density matrices via Bayesian inference. We finally use the reconstructed states to
address the influence of exchange symmetry on particle-particle entanglement in systems
of identical fermions. Using the simple notion of an Antisymmetric Negativity
we are able to separate entanglement from antisymmetrization from entanglement
induced by interaction.},
  url = {https://archiv.ub.uni-heidelberg.de/volltextserver/28329/1/DissertationJanHendrikBecher.pdf},
}