Transport through hybrid quantum dots

In order to employ solid state quantum dots as qubits, both a high degree of control over the confinement potential as well as sensitive charge detection are essential. We demonstrate that by combining local anodic oxidation with local Schottky-gates, these criteria are nicely fulfilled in the resulting hybrid device. To this end, a quantum dot with adjacent charge detector is defined. After tuning the quantum dot to contain only a single electron, we are able to observe the charge detector signal of the quantum dot state for a wide range of tunnel couplings. A detailed investigation of the Coulomb peak width (direct current through the dot) as well as the transconductance (differential signal of the QPC detector) shows agreement of the two measurement techniques which is better than their agreement with calculated line-shapes taking tunneling coupling and temperature broadening into account. For strong coupling of the dot to source and drain as well as in the finite bias regime the dot signal and the QPC signal show pronounced differences.

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