Comment on "Vindication of entanglement-based witnesses of non-classicality in hybrid systems"

TL;DR

This paper critiques recent claims about quantum-classical interaction models, demonstrating that entanglement can be generated via classical mediators and clarifying the limitations of existing no-go theorems.

Contribution

It corrects misconceptions in prior work, providing counterexamples and clarifying the scope of no-go theorems regarding entanglement generation in hybrid systems.

Findings

Classical mediators can generate quantum entanglement.

Many no-go theorems have limited applicability.

A simple example of entanglement via a classical bit is provided.

Abstract

Models of quantum-classical interactions fall into two classes: those which allow the generation of quantum entanglement via a classical mediator (such as gravity), and those which do not. Marconato and Marletto have recently sought to distinguish between these classes by claiming that known members of the first class (based on the configuration-ensemble formalism introduced by us) fail to model the mediator as a 'classical' system, and are nonlocal. We explicitly show that this claim is incorrect, and expose a large number of errors and misconceptions in their reasoning. We also point to a very simple and transparent example of the generation of entanglement between two qubits via a classical bit. It follows that there are models permitting the generation of entanglement via quantum-classical interactions that lie outside the remit of the theorem cited by Marconato and Marletto. We clarify the reasons for the limited applicability of various no-go theorems for entanglement generation.