Nuclear magnetic resonance quantum computing exploiting the pure spin state of para hydrogen

Nuclear magnetic resonance (NMR) is well-suited to implement quantum algori thms experimentally. However, there are serious problems associated with th e noisy mixed initial state that is described by the thermal equilibrium de nsity operator of NMR spectroscopy. Here we present a new strategy to drama tically increase the sensitivity of a NMR quantum computing experiment. Par a hydrogen can be used to prepare a density operator in a suitable molecule that is very close to a pure state, an improvement on the order of 10(4) c ompared to "conventional" NMR quantum computing. Our strategy is demonstrat ed experimentally solving the Deutsch-Jozsa problem based on para hydrogen and Vaska's complex. (C) 2000 American Institute of Physics. [S0021- 9606(0 0)02030-4].