Entanglement, Complexity, and Causal Asymmetry in Quantum Theories

TL;DR

This paper demonstrates that quantum entanglement introduces a fundamental causal asymmetry in quantum systems, enabling the identification of causation through complexity measures despite the time-symmetry of quantum dynamics.

Contribution

It establishes a novel link between entanglement, complexity, and causal asymmetry, providing a new method to infer causation in quantum theories.

Findings

Entanglement correlates with causal asymmetry in quantum evolution.

Complexity measures can reveal causal direction in quantum states.

A new framework for causal inference in quantum systems is proposed.

Abstract

It is often claimed that one cannot locate a notion of causation in fundamental physical theories. The reason most commonly given is that the dynamics of those theories do not support any distinction between the past and the future, and this vitiates any attempt to locate a notion of causal asymmetry -- and thus of causation -- in fundamental physical theories. I argue that this is incorrect: the ubiquitous generation of entanglement between quantum systems grounds a relevant asymmetry in the dynamical evolution of quantum systems. I show that by exploiting a connection between the amount of entanglement in a quantum state and the algorithmic complexity of that state, one can use recently developed tools for causal inference to identify a causal asymmetry -- and a notion of causation -- in the dynamical evolution of quantum systems. https://doi.org/10.1007/s10701-022-00562-0