> The problem is not copying internal states, the problem is I/O. A given instance of a quantum computation can only be queried once before it decoheres and goe

> The problem is not copying internal states, the problem is I/O. A given instance of a quantum computation can only be queried once before it decoheres and goes "poof" because the querying process itself decoheres the system. So a quantum computer can never pass the Turing test because it cannot even participate in the Turing test without destroying itself. You seem to be saying that a computer can only be called a quantum computer if it never decoheres. Or perhaps that it is only usable in some sort of batch-mode, like mainframes with punch-card decks, with each calculation cycle being a laborious one-shot affair. I have little doubt that many near-future quantum computers will be used in exactly that mode, but also that at some point thereafter their coherence/decoherence cycles will start to be measured in Hz, Khz, etc. Therefore there should in principle be no barrier to a quantum computer participating in a Turing test, or any other use-case that requires interaction.