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Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 13: Transport - Quantum Coherence and Quantum Information Systems

TT 13.10: Talk

Saturday, March 5, 2005, 11:15–11:30, TU H3027

Charge Qubits for Quantum Computation: Chances and Limitations — •Martina Hentschel1,2, Eduardo R. Mucciolo3, and Harold U. Baranger11Duke University, Durham, NC, USA — 2Universität Regensburg — 3University of Central Florida, Orlando, FL ,USA

Charge qubits realized in lateral quantum dot systems allow one to combine well-established semiconductor technologies with using the electron’s classical charge, rather than its spin, to define the computational basis. The charge qubit we consider is a ring of three identical quantum dots joined by controllable tunneling barriers with one (extra) unpaired electron in the system. A magnetic flux through the ring allows one to define the working point of the qubit such that the two lowest eigenstates are degenerate in energy and have a homogeneous charge distribution which is hoped to reduce the decoherence due to coupling to piezoelectric phonons that is of importance in a double-dot charge qubit. We demonstrate the possibility to carry out one and two qubit operations and find that one qubit operations do not require the varying of magnetic fields locally. Performing a Schrieffer-Wolf transformation we show that the swap two qubit operation can be implemented using a single pulse of appropriate length. Based on a microscopic model and a Markov approximation, we solve the resulting Redfield equation and compare the energy and phase relaxation time with the respective times of a double-dot charge qubit. Interpreting the counterintuitive result, we extend the understanding of charge qubits.

Supported in part by ARO Contract No. DAAD19-02-1-0079.

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