Causal Asymmetry of Classical and Quantum Autonomous Agents

TL;DR

This paper introduces process causal asymmetry to explain why classical autonomous agents typically become less accurate under noise, and shows that quantum memory can reverse this asymmetry, altering the direction of process simplification.

Contribution

It formalizes process causal asymmetry and demonstrates that quantum memory can reverse this asymmetry, revealing fundamental differences between classical and quantum autonomous agents.

Findings

Classical agents show increased complexity under noise due to causal asymmetry.

Quantum memory can reverse the causal asymmetry, simplifying processes in the opposite direction.

The direction of process simplification depends on whether quantum information is utilized.

Abstract

Why is it that a ticking clock typically becomes less accurate when subject to outside noise but rarely the reverse? Here, we formalize this phenomenon by introducing process causal asymmetry - a fundamental difference in the amount of past information an autonomous agent must track to transform one stochastic process to another over an agent that transforms in the opposite direction. We then illustrate that this asymmetry can paradoxically be reversed when agents possess a quantum memory. Thus, the spontaneous direction in which processes get 'simpler' may be different, depending on whether quantum information processing is allowed or not.