Werner Wegscheider

Publications (4)7.37 Total impact

• Article: Photon- and phonon-assisted tunneling in the three-dimensional charge stability diagram of a triple quantum dot array

  Floris R. Braakman, Pierre Barthelemy, Christian Reichl, Werner Wegscheider, Lieven M. K. Vandersypen
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  ABSTRACT: We report both photon- and phonon-assisted tunneling transitions in a linear array of three quantum dots, which can only be understood by considering the full three-dimensionality of the charge stability diagram. Such tunneling transitions potentially contribute to leakage of qubits defined in this system. A detailed understanding of these transitions is important as they become more abundant and complex to analyze as quantum dot arrays are scaled up.
  03/2013;
• Article: Long-range coherent coupling in a quantum dot array

  Floris R. Braakman, Pierre Barthelemy, Christian Reichl, Werner Wegscheider, Lieven M. K. Vandersypen
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  ABSTRACT: Controlling long-range quantum correlations is central to quantum computation and simulation. In quantum dot arrays, experiments so far rely on nearest-neighbour couplings only, and inducing long-range correlations requires sequential local operations. Here we show that two distant sites can be tunnel coupled directly. The coupling is mediated by virtual occupation of an intermediate site, with a strength that is controlled via the energy detuning of this site. It permits a single charge to oscillate coherently between the outer sites of a triple dot array without passing through the middle, as demonstrated through the observation of Landau-Zener-St\"uckelberg interference. The long-range coupling significantly improves the prospects of fault-tolerant quantum computation using quantum dot arrays and opens up new avenues for performing quantum simulations in nanoscale devices.
  03/2013;
• Source

  Available from: tudelft.nl

  Article: Insitu reduction of charge noise in GaAs/AlxGa1-xAs Schottky-gated devices.

  Christo Buizert, Frank H L Koppens, Michel Pioro-Ladrière, Hans-Peter Tranitz, Ivo T Vink, Seigo Tarucha, Werner Wegscheider, Lieven M K Vandersypen
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  ABSTRACT: We show that an insulated electrostatic gate can be used to strongly suppress ubiquitous background charge noise in Schottky-gated GaAs/AlGaAs devices. Via a 2D self-consistent simulation of the conduction band profile we show that this observation can be explained by reduced leakage of electrons from the Schottky gates into the semiconductor through the Schottky barrier, consistent with the effect of "bias cooling." Upon noise reduction, the noise power spectrum generally changes from Lorentzian to 1/f type. By comparing wafers with different Al content, we exclude that DX centers play a dominant role in the charge noise.
  Physical Review Letters 12/2008; 101(22):226603. · 7.37 Impact Factor
• Source

  Available from: ArXiv

  Article: In situ reduction of charge noise in GaAs/AlGaAs Schottky-gated devices

  Christo Buizert, Frank H. L. Koppens, Michel Pioro-Ladriere, Hans-Peter Tranitz, Ivo T. Vink, Seigo Tarucha, Werner Wegscheider, Lieven M. K. Vandersypen
  [show abstract] [hide abstract]
  ABSTRACT: We show that an insulated electrostatic gate can be used to strongly suppress ubiquitous background charge noise in Schottky-gated GaAs/AlGaAs devices. Via a 2-D self-consistent simulation of the conduction band profile we show that this observation can be explained by reduced leakage of electrons from the Schottky gates into the semiconductor through the Schottky barrier, consistent with the effect of "bias cooling". Upon noise reduction, the noise power spectrum generally changes from Lorentzian to $1/f$ type. By comparing wafers with different Al content, we exclude that DX centers play a dominant role in the charge noise. Comment: 4 pages, 3 figures
  08/2008;