  A new approach to the implementation of a quantum computer by high-resolution
nuclear magnetic resonance (NMR) is described. The key feature is that two or
more line-selective radio-frequency pulses are applied simultaneously. A
three-qubit quantum computer has been investigated using the 400 MHz NMR
spectrum of the three coupled protons in 2,3-dibromopropanoic acid. It has been
employed to implement the Deutsch-Jozsa algorithm for distinguishing between
constant and balanced functions. The extension to systems containing more
coupled spins is straightforward and does not require a more protracted
experiment.
