Ontological states and dynamics of discrete (pre-)quantum systems

TL;DR

This paper explores ontological states in discrete quantum systems through Cellular Automata, highlighting the challenges of maintaining ontological states under quantum-like dynamics and proposing multipartite spin systems as a potential solution.

Contribution

It introduces a class of discrete deterministic cellular automata with quantum-like features, analyzing their limitations in preserving ontological states and suggesting multipartite spin systems as a promising approach.

Findings

Discrete automata exhibit quantum-like properties at small scales.

Superposition states tend to be non-ontological in these models.

Multipartite spin systems may sustain ontological states with unitary evolution.

Abstract

The notion of ontological states is introduced here with reference to the Cellular Automaton Interpretation of Quantum Mechanics proposed by G.'t Hooft. A class of discrete deterministic "Hamiltonian" Cellular Automata is defined that has been shown to bear many features in common with continuum quantum mechanical models, however, deformed by the presence of a finite discreteness scale $l$, such that for $l\rightarrow 0$ the usual properties result -- e.g., concerning linearity, dispersion relations, multipartite systems, and Superposition Principle. We argue that within this class of models only very primitive realizations of ontological states and their dynamics can exist, since the equations of motion tend to produce superposition states that are not ontological. The most interesting, if not only way out seems to involve interacting multipartite systems composed of two-state "Ising spins", which evolve by a unitary transfer matrix. Thus, quantum like and ontological models appear side by side here, but distinguished by second-order and first-order dynamics, respectively.