WIGNER’S FRIEND AND BELL’S BEABLES

A field-theoretic version of the Wigner’s (1961) friend story illustrates how the quantum measurement problem arises for field theory. Considering spacelike separate measurements of entangled fields shows the sense in which relativistic constraints make the measurement problem particularly difficult to resolve in the context of a relativistic quantum field theory. We will consider proposals by Wigner (1961), Bloch (1967), Helwig & Kraus (1970), and Bell (1984) for resolving the measurement problem for quantum field theory and conclude by considering the possibility of giving up rich dynamical explanation in the context of a many-maps theory.