title: Bipolar spin blockade and coherent state superpositions in a triple quantum dot.
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.
authors: Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain.
authors: M
authors: M
authors: Busl
authors: G
authors: G
authors: Granger
authors: L
authors: L
authors: Gaudreau
authors: R
authors: R
authors: Sánchez
authors: A
authors: A
authors: Kam
authors: M
authors: M
authors: Pioro-Ladrière
authors: S A
authors: SA
authors: Studenikin
authors: P
authors: P
authors: Zawadzki
authors: Z R
authors: ZR
authors: Wasilewski
authors: A S
authors: AS
authors: Sachrajda
authors: G
authors: G
authors: Platero