Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 30: Quantum dots and wires: Transport properties II

HL 30.3: Talk

Wednesday, March 29, 2006, 18:45–19:00, HSZ 01

Prediction of a concrete two qubit quantum gate based on quantum wires — •Tobias Zibold¹, Andrea Bertoni², and Peter Vogl¹ — ¹Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching — ²National Research Center S3, INFM-CNR, 41100 Modena, Italy

We predict a concrete semiconductor nanostructure for a two qubit quantum gate based on ballistic transport in quantum wires. The device allows controlled entanglement and its determination from DC I-V characteristics. In contrast to the majority of proposals that use charge or spin in closed systems such as quantum dots, our device is based on open system qubits [1]. This allows for an especially simple DC write-in and read-out process. The device consists of two vertically stacked GaAs/AlGaAs 2DEGs that are depleted by external gates to form a Mach-Zehnder interferometer for ballistic electrons in each of the two layers. Each of which represents a single qubit [2]. We show that the entanglement between the two interferometers leads to controlled dephasing and can be determined from their I-V characteristics. We further show that correlation measurements of the I-V characteristics of both interferometers can be used to distinguish this mechanism of dephasing from other sources thereof. To this end we have developed a Green’s function method that allows us to calculate the ballistic current of the coupled system for a realistic, three-dimensional device structure. [1] G.B. Akguc et al., Phys. Rev. A 69, 042303 (2004). [2] A. Bertoni et al., Phys. Rev. Lett. 84, 5912 (2000).