The classical methods used by recursion theory and formal logic to block paradoxes do not work in quantum information theory. Since quantum information can exist as a coherent superposition of the classical "yes" and "no" states, certain tasks which are not conceivable in the classical setting can be performed in the quantum setting. Classical logical inconsistencies do not arise, since there exist fixed point states of the diagonalization operator. In particular, closed timelike curves need not be eliminated in the quantum setting, since they would not lead to any paradoxical outcome controllability. Quantum information theory can also be subjected to the treatment of inconsistent information in databases and expert systems. It is suggested that any two pieces of contradicting information are stored and processed as coherent superposition. In order to be tractable, this strategy requires quantum computation.
paradox.texThis letter introduces two novel features of quantum information theory. Physically, it is shown how quantum information allows the consistent implementation of nonlocal correlations. Technically, a diagonalization operator is used to compute consistent fixed point solutions to classical "paradoxical" tasks. The implications for quantum recursion theory [1] and algorithmic information theory [2] as well as for database applications will only be shortly sketched.Classical information theory (e.g., [3]) is based on the bit as fundamental atom. This classical bit, henceforth called cbit, is in one of two classical states.