Schr\"odinger's Cat: Where Does The Entanglement Come From?

TL;DR

This paper analyzes Schrödinger's cat paradox using quantum information theory, showing that the atom and cat are connected only through classical channels and cannot become entangled through local operations and classical communication.

Contribution

It introduces a quantum networks formalism to clarify the origin of entanglement in the paradox, emphasizing the classical nature of the information flow.

Findings

Atom and cat are connected only via classical information channels.

No local operations can entangle the initially separable atom and cat.

The paradox is reframed with a focus on classical information transfer.

Abstract

Schr\"odinger's cat is one of the most striking paradoxes of quantum mechanics that reveals the counterintuitive aspects of the microscopic world. Here, I discuss the paradox in the framework of quantum information. Using a quantum networks formalism, I analyse the information flow between the atom and the cat. This reveals that the atom and the cat are connected only through a classical information channel: the detector clicks $\rightarrow$ the poison is released $\rightarrow$ the cat is killed. No amount of local operations and classical communication can entangle the atom and the cat, which are initially in a separable state. This casts a new light on the paradox.