InAs/GaAs single-electron quantum dot qubit

The time evolution of the quantum mechanical state of an electron is calcul ated in the framework of the effective-mass envelope function theory for an InAs/GaAs quantum dot. The results indicate that the superposition state e lectron density oscillates in the quantum dot, with a period on the order o f femtoseconds. The interaction energy E-ij between two electrons located i n different quantum dots is calculated for one electron in the ith pure qua ntum state and another in the jth pure quantum state. We find that E-11]E-1 2]E-22, and E-ij decreases as the distance between the two quantum dots inc reases. We present a parameter-phase diagram which defines the parameter re gion for the use of an InAs/GaAs quantum dot as a two-level quantum system in quantum computation. A static electric field is found to efficiently pro long the decoherence time. Our results should be useful for designing the s olid-state implementation of quantum computing. (C) 2001 American Institute of Physics.