It from Qubit Summer School
I enumerate the cases in 2d CFT when the modular hamiltonian (log of the reduced density matrix) may be written as an appropriate integral over the energy-momentum tensor times a local weight. This includes known examples as well as new time-dependent ones. In all these cases the entanglement spectrum is that of an appropriate boundary CFT. I point out the obstruction to the existence of such a result for more complicated bipartitions of the space. This is joint work with Erik Tonni
In this talk I consider the following principle that one may impose on any physical theory T:
"If an agent uses T to describe a system which includes another agent who herself uses T then no logical contradictions should arise.”
I then propose a gedankenexperiment, which can be regarded as an extension of the Wigner’s Friend experiment, to test whether this principle holds for quantum mechanics. The conclusion is that this is indeed the case for “plain" quantum theory, but that the principle is violated by many of its common interpretations and extensions.