Probabilities from Quantum States, or Quantum States from Probabilities?

          @misc{ pirsa_PIRSA:09100091,
            doi = {10.48660/09100091},
            url = {https://pirsa.org/09100091},
            author = {Barnum, Howard},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Probabilities from Quantum States, or Quantum States from Probabilities?},
            publisher = {Perimeter Institute},
            year = {2009},
            month = {oct},
            note = {PIRSA:09100091 see, \url{https://pirsa.org}}
          }
          

Abstract

I will consider various attempts to derive the quantum probabilities from the HIlbert space formalism within the many-worlds interpretation, and argue that they either fail, or depend on tacit probabilistic assumptions. The main problem with the project is that it is difficult to understand what the state of system X is psi even *means* without already supposing some probabilistic link to definite observed or observable phenomena involving X. I will argue it is better to conceive of quantum states as *representations* of empirically inferred probabilities for quantum processes associated with definite observable phenomena, accepting all the issues this raises concerning what exactly are to count as observable outcomes, and relatedly, what as real, as an unavoidable conundrum but also a potential source of progress in the evolution of physical theory.