Bipolar spin blockade and coherent state superpositions in a triple quantum dot

Authors:
  • GGG. Granger
    G. Granger
  • LGL. Gaudreau
    L. Gaudreau
  • AKA. Kam
    A. Kam
  • MPM. Pioro-Ladrière
    M. Pioro-Ladrière
  • SSS. A. Studenikin
    S. A. Studenikin
  • PZP. Zawadzki
    P. Zawadzki
  • ZWZ. R. Wasilewski
    Z. R. Wasilewski
  • ASA. S. Sachrajda
    A. S. Sachrajda
  • GPG. Platero
    G. Platero
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Abstract
Spin qubits based on interacting spins in double quantum dots have been demonstrated successfully. Readout of the qubit state involves a conversion of spin to charge information, which is universally achieved by taking advantage of a spin blockade phenomenon resulting from Pauli's exclusion principle. The archetypal spin blockade transport signature in double quantum dots takes the form of a rectified current. At present, more complex spin qubit circuits including triple quantum dots are being developed. Here we show, both experimentally and theoretically, that in a linear triple quantum dot circuit the spin blockade becomes bipolar with current strongly suppressed in both bias directions and also that a new quantum coherent mechanism becomes relevant. In this mechanism, charge is transferred non-intuitively via coherent states from one end of the linear triple dot circuit to the other, without involving the centre site. Our results have implications for future complex nanospintronic circuits.
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