Witnessing non-objectivity in the framework of strong quantum Darwinism

TL;DR

This paper introduces a new method to detect non-objectivity in quantum systems, enabling more feasible experimental tests of quantum Darwinism and the quantum-to-classical transition using photonic simulations.

Contribution

It proposes a subspace-dependent objectivity witness and a photonic experimental scheme to detect non-objectivity without full quantum state tomography.

Findings

The witness can identify non-objectivity in quantum states.

The proposed photonic simulation demonstrates practical implementation.

The method simplifies experimental verification of quantum Darwinism.

Abstract

Quantum Darwinism is a compelling theory that describes the quantum-to classical transition as the emergence of objectivity of quantum systems. Spectrum broadcast structure and strong quantum Darwinism are two extensions of this theory with emphasis on state structure and information respectively. The complete experimental verification of these three frameworks, however, requires quantum state tomography over both the system and accessible environments, thus limiting the feasibility and scalability of experimental tests. Here, we introduce a subspace-dependent objectivity operation and construct a witness that detects non-objectivity by comparing the dynamics of the system-environment state with and without the objectivity operation. We then propose a photonic experimental simulation that implements the witnessing scheme. Our work proposes a route to further experimental exploration of the quantum to classical transition.