Generating Multimode Entangled Microwaves with a Superconducting Parametric Cavity

TL;DR

This paper demonstrates a method to generate and characterize multimode entangled microwave states using a superconducting cavity with programmable entanglement structures, fully measured via covariance matrices and calibrated with an in situ source.

Contribution

It introduces a versatile approach to produce and analyze multimode entangled microwaves with full covariance matrix characterization and in situ calibration.

Findings

Successfully generated multimode entangled microwave states

Demonstrated full inseparability and tripartite entanglement

Method is extensible to more modes

Abstract

In this Letter, we demonstrate the generation of multimode entangled states of propagating microwaves. The entangled states are generated by parametrically pumping a multimode superconducting cavity. By combining different pump frequencies, applied simultaneously to the device, we can produce different entanglement structures in a programable fashion. The Gaussian output states are fully characterized by measuring the full covariance matrices of the modes. The covariance matrices are absolutely calibrated using an in situ microwave calibration source, a shot noise tunnel junction. Applying a variety of entanglement measures, we demonstrate both full inseparability and genuine tripartite entanglement of the states. Our method is easily extensible to more modes.