Living in a Superposition

TL;DR

This paper models a quantum universe with a double-slit setup, demonstrating that after passing through the slits, the universe exists in a superposition of distinguishable histories, and explores implications for quantum cosmology.

Contribution

It applies modern quantum mechanics of closed systems to a cosmological model, illustrating how superpositions of histories arise in a universe with a double-slit setup.

Findings

The universe's quantum state becomes a superposition after passing through the slits.

The model explains how observers experience definite outcomes despite superpositions.

Discussion links the model to broader quantum cosmological theories.

Abstract

This essay considers a model quantum universe consisting of a very large box containing a screen with two slits and an observer (us) that can pass though the slits. We apply the modern quantum mechanics of closed systems to calculate the probabilities for alternative histories of how we move through the universe and what we see. After passing through the screen with the slits, the quantum state of the universe is a superposition of classically distinguishable histories. We are then living in a superposition. Some frequently asked questions about such situations are answered using this model. The model's relationship to more realistic quantum cosmologies is briefly discussed.