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HL: Fachverband Halbleiterphysik

HL 24: Quantum dots and wires: Transport properties II

HL 24.11: Vortrag

Dienstag, 27. März 2007, 16:45–17:00, H15

Theory of quantum computation with all-electronic Mach-Zehnder interferometers — •Tobias Zibold and Peter Vogl — Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching

We present a realistic theoretical analysis of an all-electronic Mach-Zehnder interferometer realized by two electrostatically defined quantum wires in a GaAs/AlGaAs 2DEG. In contrast to electronic Mach-Zehnder interferometers based on quantum Hall edge channels, no magnetic fields are employed. The phase shift between the quantum wires can be controlled electrostatically by the same external gates that also define the quantum wires. This allows for a simple layout of the gates with none of the lateral scales below 40 nm. We calculate the ballistic I-V characteristics of the fully three-dimensional, open device using a single-band effective mass description for the electronic Hamiltonian including the Hartree potential self-consistently. We show that the interferometer can be employed as a single qubit gate. The DC I-V characteristics exhibit multiple pronounced switches that can be attributed to rotations of the qubit on the Bloch sphere. We find that these rotations depend critically on the crossing of two resonances in the coupling windows that connect the quantum wires and act as beam-splitters. Thus, the size of the coupling windows is most important for the operation of the Mach-Zehnder interferometer as a single qubit gate.