Macroscopic Superposition States in Isolated Quantum Systems

TL;DR

This paper demonstrates that large isolated quantum systems naturally evolve into macroscopic superposition states over time, based on von Neumann's Quantum Ergodic Theorem, highlighting their ubiquity in quantum dynamics.

Contribution

It shows that macroscopic superpositions are a common outcome in isolated quantum systems under broad conditions, connecting quantum evolution to many-worlds interpretation.

Findings

Large systems evolve into superpositions of macroscopically distinct states.

Superpositions are a generic consequence of quantum ergodicity.

Connection established between quantum superpositions and many-worlds theory.

Abstract

For any choice of initial state and weak assumptions about the Hamiltonian, large isolated quantum systems undergoing Schrodinger evolution spend most of their time in macroscopic superposition states. The result follows from von Neumann's 1929 Quantum Ergodic Theorem. As a specific example, we consider a box containing a solid ball and some gas molecules. Regardless of the initial state, the system will evolve into a quantum superposition of states with the ball in macroscopically different positions. Thus, despite their seeming fragility, macroscopic superposition states are ubiquitous consequences of quantum evolution. We discuss the connection to many worlds quantum mechanics.