Some time far into the future, humans have made the technology breakthroughs to construct decoherence-proof reversible quantum computers with quantum fault tolerance. They have also solved the hard AI problem. They program a quantum conscious being on such a computer and also a two state quantum system. The quantum conscious being is programmed to entangle with the quantum system, measuring it. The rules of the Copenhagen interpretation tell us the state of the quantum system happened. The programmers reverse the program, undoing the measurement, with all the memory wiped clean. Did the quantum system unhappen?
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