The hyperfine energy spectrum of31P donors in a silicon NMR quantum computer

The effect of an electric field on the hyperfine interaction constant (HIC) of a donor atom is considered within the silicon quantum computer model. The field is produced by the potential of a circular (disk-shaped) or strip gate. A spread in the HIC values because of inaccurately placing donor atoms under the gate is estimated. The energy spectrum of the electron-nuclear spin system for two interacting donor atoms with different HICs is evaluated. Two pairs of levels anticrossing in the ground state are shown to exist.