# Updating the Born rule

## TL;DR

This paper proposes a new, more fundamental probability rule in quantum theory that unifies the Born rule and collapse rule, offering a foundation for knowledge-based interpretations of quantum mechanics.

## Contribution

It derives a unified probability rule that replaces the separate Born and collapse rules, providing a new foundation for interpreting quantum theory.

## Key findings

- The new rule subsumes both the Born and collapse rules.
- It offers a rigorous basis for informational interpretations.
- The approach challenges traditional views on quantum measurement.

## Abstract

Despite the tremendous empirical success of quantum theory there is still widespread disagreement about what it can tell us about the nature of the world. A central question is whether the theory is about our knowledge of reality, or a direct statement about reality itself. Regardless of their stance on this question, current interpretations of quantum theory regard the Born rule as fundamental and add an independent state-update (or "collapse") rule to describe how quantum states change upon measurement. In this paper we present an alternative perspective and derive a probability rule that subsumes both the Born rule and the collapse rule. We show that this more fundamental probability rule can provide a rigorous foundation for informational, or "knowledge-based", interpretations of quantum theory.