A method is proposed to prepare an effective pure state corresponding to th
e pure state \0)\0) (0) for any number of spins on a nuclear magnetic reson
ance quantum computer, where \0) stands for the spin-up state of a nuclear
spin. The method is based on the spatial labeling proposed by Gory et al. [
Proc. Natl. Acad. Sci. USA 94, 1634 (1997)].