arXiv:2003.07464quant-ph
Physics and Metaphysics of Wigner's Friends: Even performed pre-measurements have no results
Abstract
"The unambiguous account of proper quantum phenomena must, in principle, include a description of all relevant features of experimental arrangement" (Bohr). The measurement process is composed of pre-measurement (quantum correlation of the system with the pointer variable), and an irreversible decoherence via interaction with an environment. The system ends up in a probabilistic mixture of the eigenstates of the measured observable. For the pre-measurement stage, any attempt to introduce an 'outcome' leads, as we show, to a logical contradiction, $1=i$. This nullifies claims that a modified concept of Wigner's Friend, who just pre-measures, can lead to valid results concerning quantum theory.
> The state's evolution will be completely equivalent to (a linear superposition of) the evolution of |x>|x> and |y>|y>. That's a physically observable fact that's independent of your choice of basis (it's less obvious in the |z>/|w> basis, but it's still true). Of course the…
OrlanthaiView on HNParent context
> Of course the state can be written in the form |xx> + |yy>. I never denied that. The point is that it can be written in other forms. So it's equally correct to say we'd "experience" |zz> + |ww> + |zw> + |wz> as to say we'd experience |xx> + |yy> so there's no reason to say…
lmmView on HNParent context