Time-Symmetric Electrodynamics and Quantum Measurement

Abstract

A phenomenon such as the instantaneous collapse of the wavefunction associated with the measurement process seems necessary in order to predict results from quantum mechanics. That such a postulate gives correct results for spatially ex-tended quantum optical EPR type experiments, as has been experimentally verified, makes it somewhat of an enigma, because an instantaneous collapse does not have a Lorentz covariant description. Philosophical arguments based on logical positivism, which involve abandoning the concept of physical reality, have been used to circumvent this difficulty, but to many these are not satisfying and attempts are still being made to understand the experiments in terms of real physical processes which permit a specification of the quantum state during all evolution stages before the measurement takes place. The simplest type of experiment concerns the detection of a photon from a two-level atom a by a detector at a distance r away. A question which might be asked is - does the detection or measurement have a real physical influence which causes a to jump to the ground state and, if so, when does this occur, at the same time as detection, or a time r/c before or at r/c after detection?