Aharonov-Bohm phase as quantum gate in two-electron charge qubits

A. Weichselbaum and S. E. Ulloa
Phys. Rev. B 70, 195332 – Published 22 November 2004

Abstract

We analyze the dynamics of a ground state two-level system built on the spatial distribution of the system wave function and designed to be well-separated from the remainder of the state space. With a total of two operative electrons on a planar array of quantum dots coupled capacitively to a set of external voltage gates, the system is modeled using an extended Hubbard Hamiltonian. The voltage dependence of the low-energy singlet and triplet states is analyzed, respectively, using the Feshbach formalism. Coherent operation of the array is studied with respect to single quantum bit operations. One quantum gate is implemented via voltage controls, while for the necessary second quantum gate, a uniform external magnetic field is introduced. The Aharonov-Bohm phases on the closed loop tunnel connections in the array are used to effectively suppress the tunneling, despite a constant tunneling amplitude in the structure. This allows one to completely stall the qubit in any arbitrary quantum superposition, providing full control of this interesting quantum system.

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  • Received 2 March 2004

DOI:https://doi.org/10.1103/PhysRevB.70.195332

©2004 American Physical Society

Authors & Affiliations

A. Weichselbaum and S. E. Ulloa

  • Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701, USA

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Issue

Vol. 70, Iss. 19 — 15 November 2004

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