  Recently, the quantum information processing power of closed timelike curves
have been discussed. Because the most widely accepted model for quantum closed
timelike curve interactions contains ambiguities, different authors have been
able to reach radically different conclusions as to the power of such
interactions. By tracing the information flow through such systems we are able
to derive equivalent circuits with unique solutions, thus allowing an objective
decision between the alternatives to be made. We conclude that closed timelike
curves, if they exist and are well described by these simple models, would be a
powerful resource for quantum information processing.
