Quantum prescriptions are more ontologically distinct than they are operationally distinguishable

TL;DR

This paper introduces a new ontological concept called bounded ontological distinctness and demonstrates that quantum preparations and transformations exhibit excess ontological distinctness, surpassing classical distinguishability, with implications for quantum communication tasks.

Contribution

It formulates bounded ontological distinctness as a principle and empirically shows quantum violations, establishing a novel ontological perspective on quantum phenomena.

Findings

Quantum preparations violate bounded ontological distinctness.

Quantum transformations exhibit excess ontological distinctness.

Quantum violations impact other ontological principles and enable new communication tasks.

Abstract

Based on an intuitive generalization of the Leibniz principle of `the identity of indiscernibles', we introduce a novel ontological notion of classicality, called bounded ontological distinctness. Formulated as a principle, bounded ontological distinctness equates the distinguishability of a set of operational physical entities to the distinctness of their ontological counterparts. Employing three instances of two-dimensional quantum preparations, we demonstrate the violation of bounded ontological distinctness or excess ontological distinctness of quantum preparations, without invoking any additional assumptions. Moreover, our methodology enables the inference of tight lower bounds on the extent of excess ontological distinctness of quantum preparations. Similarly, we demonstrate excess ontological distinctness of quantum transformations, using three two-dimensional unitary transformations. However, to demonstrate excess ontological distinctness of quantum measurements, an additional assumption such as outcome determinism or bounded ontological distinctness of preparations is required. Moreover, we show that quantum violations of other well-known ontological principles implicate quantum excess ontological distinctness. Finally, to showcase the operational vitality of excess ontological distinctness, we introduce two distinct classes of communication tasks powered by excess ontological distinctness.