Causal unitary qubit model of black hole evaporation

TL;DR

This paper introduces a simple four-qubit unitary model for black hole evaporation that explicitly preserves unitarity and causality, providing a basic approximation of the Page curve.

Contribution

It presents a novel four-qubit quantum circuit model of black hole evaporation emphasizing unitarity and causality, which are often challenging to reconcile.

Findings

Model maintains explicit unitarity.

Model enforces causality, preventing information transfer from black hole interior.

Approximate Page curve derived from entanglement entropy.

Abstract

A new simple qubit model of black hole evaporation is proposed. The model operates on four qubits and is defined in terms of quantum gates and a quantum circuit. The chief features of the model include explicit unitarity and (most notably) causality which is understood as the impossibility of the transfer of information from the interior of the black hole through its horizon. The corresponding von Neumann entanglement entropy yields a crude (four-qubit) approximation of the Page curve.