We present a classical model for bulk-ensemble NMR quantum computation: the quantum
state of the NMR sample is described by a probability distribution over the orientations of
classical tops, and quantum gates are described by classical transition probabilities. All
NMR quantum computing experiments performed so far with three quantum bits can be
accounted for in this classical model. After a few entangling gates, the classical model
suffers an exponential decrease of the measured signal, whereas there is no corresponding …

We present a classical model for bulk-ensemble NMR quantum computation: the quantum
state of the NMR sample is described by a probability distribution over the orientations of
classical tops, and quantum gates are described by classical transition probabilities. All
NMR quantum computing experiments performed so far with three quantum bits can be
accounted for in this classical model. After a few entangling gates, the classical model
suffers an exponential decrease of the measured signal, whereas there is no corresponding …