Reply To: Counterfactual communication protocol

Lev Vaidman

Dear Travis,

Yes, you are on the right track. Locally, there is only local density matrix. It captures all information about what is there. And it cannot be changed by action at a distance.
But, all local density matrices do not exhaust all the ontology. Wave function is more than this. And in some sense it is non-local (entanglement etc.). However, local density matrix is certainly real as it ALL what is in a particular location. If something in this location entangled with something in other location, local interaction might lead to entanglement to more systems, but no change happens nonlocally: no action at a distance!
I am preparing a talk “Ontology of the wave function”, Saig, July 22. If it will be recorded in some way I’ll send you a link.

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