h1

% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Varvelis:967997,
      author       = {Varvelis, Evangelos},
      othercontributors = {DiVincenzo, David and Hassler, Fabian},
      title        = {{M}any-body localization for decoherence protected quantum
                      memory},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2023-08380},
      pages        = {1 Online-Ressource : Illustrationen, Diagramme},
      year         = {2023},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, RWTH Aachen University, 2023},
      abstract     = {In recent years, the field of quantum information has
                      witnessed remarkable progress through the utilization of
                      superconducting qubits. Nonetheless, despite these
                      advancements, significant hurdles persist when it comes to
                      scaling up these systems. One critical challenge that this
                      thesis aims to tackle is the phenomenon of decoherence,
                      whereby a quantum system behaves akin to a classical system
                      in thermal equilibrium. However systems can avoid
                      thermalization if they are in the many-body localized phase.
                      The main objective of this thesis is to investigate the
                      potential of MBL in protecting quantum memories from
                      decoherence. We pursue a two-fold approach: firstly, we
                      establish the existence of a thermal to MBL phase transition
                      in disordered transmon arrays. To achieve this, we employ
                      well-established diagnostics such as level spacing
                      distribution and inverse participation ratio (IPR).
                      Additionally, we introduce a new diagnostic tool called the
                      Walsh-Hadamard coefficients, which reinforce the findings of
                      IPR in a basis-independent manner. We apply these
                      diagnostics to both 1D and 2D transmon arrays with Gaussian
                      disorder, as well as chains with designed frequency patterns
                      using the LASIQ technique. Furthermore, we demonstrate that
                      disorder-free systems can also exhibit MBL by compensating
                      for the absence of disorder through the utilization of
                      quasi-periodic frequency patterns. Surprisingly, we find
                      that these systems not only achieve localization, but also
                      surpass the localization observed in comparable systems with
                      Gaussian disorder. Finally, we develop a perturbation theory
                      scheme that enables the determination of the Walsh-Hadamard
                      coefficients for large transmon lattices, which are
                      comparable to experimental devices.},
      cin          = {135220 / 130000 / 080043},
      ddc          = {530},
      cid          = {$I:(DE-82)135220_20140620$ / $I:(DE-82)130000_20140620$ /
                      $I:(DE-82)080043_20160218$},
      pnm          = {EXC 2004: Matter and Light for Quantum Computing (ML4Q)
                      (390534769)},
      pid          = {G:(BMBF)390534769},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2023-08380},
      url          = {https://publications.rwth-aachen.de/record/967997},
}