Cause and Effect in the Pilot-Wave Interpretation of Quantum Mechanics

Abstract

In the de Broglie—Bohm pilot-wave interpretation of quantum mechanics (QM), the two degrees of freedom associated with a system are its wave function and configuration (i.e., point in configuration space). From a purely dynamical point of view, neither has priority over the other, and it is tempting to treat the interpretation as having a genuinely dualistic ontology — involving both ‘ψ-fields’ and corpuscles. (We shall use the term ‘corpuscle’ to designate the hypothetical de Broglie—Bohm point particle, the words ‘system’ and ‘particle’ meaning what they do in standard QM.) In so far as the pilot-wave interpretation provides a ‘causal’ picture, it is in terms of the action of the ψ-field on its associated corpuscle(s). How is this action to be understood? In his admirable 1993 survey of the pilot-wave interpretation, Holland writes that

... the manner in which the ψ-field couples to the particle [i.e., corpuscle] via a quantum force does not on the face of it involve any concepts of cause and effect beyond those of classical physics. It is not essentially different from the action of an electromagnetic field on a charged particle, or a gravitational field on a massive particle (although there is no obvious ‘quantum charge’ associated with the particle which responds to the quantum potential ...). (Holland 1993, 83)