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.
- Received 2 March 2004
DOI:https://doi.org/10.1103/PhysRevB.70.195332
©2004 American Physical Society