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@PHDTHESIS{Kammerloher:841219,
      author       = {Kammerloher, Eugen},
      othercontributors = {Bluhm, Jörg and Bougeard, Dominique},
      title        = {{I}mproving the output signal of charge readout for quantum
                      computing in electrostatically defined quantum dots with a
                      new sensing dot concept},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2022-01567},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2022},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, RWTH Aachen University, 2022},
      abstract     = {To facilitate scaleable quantum systems beyond the NISQ
                      era, it is imperative to minimize the heat load of a qubit
                      readout operation and provide a well scaleable readout
                      periphery. Baseband readout, using transistor circuits in
                      close proximity to the qubit, is a promising candidate for a
                      well scaleable and low power consumption approach to this
                      challenge. The sensing dot is currently the most sensitive
                      sensor for readout in solid state spin qubits. However, in
                      conventional sensing dots, the output swing is limited by
                      negative feedback of a reservoir capacitance, which can
                      capacitively shunt the charge signal. In this thesis, we
                      theoretically develop and experimentally demonstrate a
                      proximal charge sensor, termed ASD, that remedies this
                      effect. In the ASD the source and drain reservoirs are
                      arranged asymmetrically, so that the relevant reservoir
                      capacitance is greatly reduced. We perform electrostatic
                      simulations, in the context of electrostatically defined
                      quantum dots in heterostructures and evaluate several gate
                      layouts, with the goal to establish an ASD demonstrator
                      layout. Since the ASD requires complex gate electrode
                      shapes, we develop a software package, termed comsolkit, to
                      aid in the gate layout creation process. We find a well
                      tunable gate layout and estimate the drain capacitance
                      reduction to be nearly 40 times, compared to a conventional
                      sensing dot, when neglecting disorder or broadening effects.
                      We perform measurements on several ASD samples, that
                      validate the ASD concept, by reducing the drain capacitance
                      by a factor of $13\pm 1$ at a bias of $V_{SD}\geq
                      4.5\,\text{mV}$. We also demonstrate successful charge
                      readout of a nearby qubit-like double dot, using the current
                      biased ASD, achieving a $(3.0\pm 0.2)\,\text{mV}$ voltage
                      swing, in distinguishing the two relevant charge states,
                      which substantially improves the response compared to
                      conventional sensing dots. We perform simulations to
                      estimate the benefits of the ASD in a baseband readout
                      configuration, for different transistor technologies and
                      implementation scenarios.The ASD achieves sensitivities of
                      $4\,\mu e/\sqrt{\text{Hz}}$ at MHz bandwidths, for a high
                      integration scenario and realistic transistor parameters,
                      extracted from cold transistor characterization
                      measurements, when excluding $1/f$ transistor noise, which
                      is comparable to highly sensitive superconducting RF-SETs.
                      Including a conservative FET $1/f$ noise model, the ASD
                      achieves $82\,\mu e/\sqrt{\text{Hz}}$, which is competitive
                      with RF-SET readout.},
      cin          = {132210 / 130000},
      ddc          = {530},
      cid          = {$I:(DE-82)132210_20140620$ / $I:(DE-82)130000_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2022-01567},
      url          = {https://publications.rwth-aachen.de/record/841219},
}