"they seem to assume that all the photons' degrees of freedom are described by pure states according to both observers. This seems wrong to me. The observation

"they seem to assume that all the photons' degrees of freedom are described by pure states according to both observers. This seems wrong to me. The observation of the photons by Wigner's friend creates an entanglement with the degrees of freedom in the friend's body, so the state of the photons themselves become mixed according to Wigner (I mean the external observer), not pure. So I think that when these things are done correctly, it's not possible to find this kind of a "contradiction" in practice." https://motls.blogspot.com/2019/03/six-photons-claimed-to-prove-that.html https://motls.blogspot.com/2019/03/six-photons-claimed-to-pr...