Epistemic Boundaries and Quantum Uncertainty: What Local Observers Can (Not) Predict

TL;DR

This paper investigates whether post-quantum theories can surpass quantum uncertainty in prediction, concluding that fundamental limitations exist unless intersubjectivity is violated, revealing an epistemic boundary among observers.

Contribution

It formally demonstrates that under no-signalling and reliable intersubjectivity, quantum uncertainty cannot be surpassed, but allows for subjective predictive advantage if intersubjectivity fails.

Findings

No-go theorem for predictive advantage under standard assumptions

Existence of subjective predictive advantage when intersubjectivity is violated

Quantum uncertainty as a fundamental limit on predictability

Abstract

One of quantum theory's salient features is its apparent indeterminism, i.e. measurement outcomes are typically probabilistic. We formally define and address whether this uncertainty is unavoidable or whether post-quantum theories can offer a predictive advantage while conforming to the Born rule on average. We present a no-go claim combining three aspects: predictive advantage, no-signalling, and reliable intersubjectivity between quantum observers. The results of the analysis lead to the conclusion that there exists a fundamental limitation on genuine predictive advantage. However, we uncover a fascinating possibility: When the assumption of reliable intersubjectivity between different observers is violated, subjective predictive advantage can, in principle, exist. This, in turn, entails an epistemic boundary between different observers of the same theory. The findings reconcile us to quantum uncertainty as an aspect of limits on Nature's predictability.