Photonic multipartite entanglement conversion using nonlocal operations

TL;DR

This paper introduces a linear optical setup for converting multipartite entangled states in quantum networks using nonlocal operations, enabling state transformation without full access to the states.

Contribution

It presents a novel, flexible linear optical gate for converting multipartite entangled states under restricted access, advancing distributed quantum computation and communication.

Findings

Successfully converts four-qubit entangled states, such as cluster to GHZ and Dicke states.

Demonstrates integration of the gate into extended graph state networks.

Shows generation of quantum correlations without entanglement.

Abstract

We propose a simple setup for the conversion of multipartite entangled states in a quantum network with restricted access. The scheme uses nonlocal operations to enable the preparation of states that are inequivalent under local operations and classical communication, but most importantly does not require full access to the states. It is based on a flexible linear optical conversion gate that uses photons, which are ideally suited for distributed quantum computation and quantum communication in extended networks. In order to show the basic working principles of the gate, we focus on converting a four-qubit entangled cluster state to other locally inequivalent four-qubit states, such as the GHZ and symmetric Dicke state. We also show how the gate can be incorporated into extended graph state networks, and can be used to generate variable entanglement and quantum correlations without entanglement but nonvanishing quantum discord.