Collapse Theory

Sang Jae Yun

To resolve the quantum measurement problem, we propose an objective collapse theory in which both the wavefunction and the process of collapse are regarded as ontologically objective. The theory, which we call the entangling-speed-threshold theory, postulates that collapse occurs when the entangling speed of a system reaches a threshold, and the collapse basis is determined so as to eliminate the entangling speed and to minimize its increasing rate. Using this theory, we provide answers to the questions of where and when collapse occurs, how the collapse basis is determined, what systems are (in other words, what the actual tensor product structure is), and what determines the observables. We also explain how deterministic classical dynamics emerges from indeterministic quantum collapse, explaining the quantum-to-classical transition. In addition, we show that the theory guarantees energy conservation to a high accuracy. We apply the theory to a macroscopic flying body such as a bullet in the air, and derive a satisfactory collapse basis that is highly localized in both position and momentum, consistent with our everyday observation. Finally, we suggest an experiment that can verify the theory.

W. Michael Dickson

Travis Norsen

Peter J. Lewis

The collapse postulate in quantum mechanics is problematic. In standard presentations of the theory, the state of a system prior to a measurement is a sum of terms, with one term representing each possible outcome of the measurement. Many dynamical collapse theories imply that the quantum wavefunction is fundamental, and that particles are just a temporary “bunching up” of the fundamental wave-like entity. Quantum mechanics is often taken to be an indeterministic theory. Quantum mechanics represents the state of a system in various ways, but the representation that is most perspicuous for understanding collapse theories uses a wavefunction. Consistency with special relativity is, therefore, a problem for dynamical collapse theories, but perhaps not an insuperable one. Some have argued that the wavefunction needs to be supplemented to counteract the effects of the novel quantum vagueness introduced by dynamical collapse theories. The ontological consequences of dynamical collapse theories remain an area of active debate.

Richard Goodman, Richard Goodman

The Collapse Theorem

Roderich Tumulka

Collapse theories are versions of quantum mechanics according to which the collapse of the wave function is a real physical process. They propose precise mathematical laws to govern this process and to replace the vague conventional prescription that a collapse occurs whenever an "observer" makes a "measurement." The "primitive ontology" of a theory (more or less what Bell called the "local beables") are the variables in the theory that represent matter in space-time. There is no consensus about whether collapse theories need to introduce a primitive ontology as part of their definition. I make some remarks on this question and point out that certain paradoxes about collapse theories are absent if a primitive ontology is introduced.