Multipartite entanglement in a Josephson Junction Laser

TL;DR

This paper investigates how a Josephson junction laser can generate multipartite and bipartite microwave entanglement among cavity modes using a quadratic Hamiltonian model, revealing block-structured entanglement patterns.

Contribution

It introduces a model analyzing Gaussian entanglement in a Josephson photonics system, highlighting the emergence of multipartite entanglement without ac excitation.

Findings

Modes form entangled blocks within the system.

Bipartite entanglement occurs within these blocks.

Tripartite entanglement is present but limited to specific Josephson energies.

Abstract

We analyse the entanglement in a model Josephson photonics system in which a dc voltage-biased Josephson junction couples a collection of cavity modes and populates them with microwave photons. Using an approximate quadratic Hamiltonian model, we study the Gaussian entanglement that develops between the modes as the Josephson energy of the system is increased. We find that the modes in the system fall into a series of blocks, with bipartite entanglement generated between modes within a given block. Tripartite entanglement between modes within a given block is also widespread, though it is limited to certain ranges of the Josephson energy. The system could provide an alternative route to generating multimode microwave entanglement, an important resource in quantum technologies, without the need for ac excitation.