Unobservable causal loops as a way to explain both the quantum computational speedup and quantum nonlocality

We consider the reversible processes between two one-to-one correlated measurement outcomes which underlie both problem solving and quantum nonlocality. In former case, are setting solution of problem; in latter, they those measuring a pair maximally entangled observables whose subsystems space separate. argue that description these mathematically describes correlation but leaves causal structure physically ensures it free violating time symmetry required process. It would therefore be incomplete could completed by symmetrizing it. This is done assuming measurements evenly contribute to selecting outcomes. Time symmetrization ordinary unaltered shows superposition unobservable time-symmetrization instances completely defined. Each instance loop: Causation goes from initial final outcome then back outcome. speedup, all as if solver knew advance half information about she will produce future use this knowledge with fewer computation steps. nonlocality, on either subsystem retrocausally locally changes state when were not yet spatially causes