Realizing a deterministic source of multipartite-entangled photonic qubits

Jean-Claude Besse,Arne Wulff,Abdulkadir Akin,Graham J Norris,Paul Magnard,Lucien Wernli,Adrian Copetudo,Daniel Malz,Kevin Reuer,Christopher Eichler,Mihai Gabureac,Andreas Wallraff,J Ignacio Cirac,Michele C Collodo

doi:10.1038/s41467-020-18635-x

Abstract

Sources of entangled electromagnetic radiation are a cornerstone in quantum information processing and offer unique opportunities for the study of quantum many-body physics in a controlled experimental setting. Generation of multi-mode entangled states of radiation with a large entanglement length, that is neither probabilistic nor restricted to generate specific types of states, remains challenging. Here, we demonstrate the fully deterministic generation of purely photonic entangled states such as the cluster, GHZ, and W state by sequentially emitting microwave photons from a controlled auxiliary system into a waveguide. We tomographically reconstruct the entire quantum many-body state for up to N = 4 photonic modes and infer the quantum state for even larger N from process tomography. We estimate that localizable entanglement persists over a distance of approximately ten photonic qubits.

Highlights

Sources of entangled electromagnetic radiation are a cornerstone in quantum information processing and offer unique opportunities for the study of quantum many-body physics in a controlled experimental setting
The probabilistic nature of such schemes is a major obstacle when scaling to larger systems, which has motivated the study of deterministic sources of entangled photonic states more recently[8,9,10]
A final SWAP operation is required to disentangle the photonic qubits from the auxiliary system by bringing the latter back to its ground state jgi, thereby rendering the generation of the final photonic state jψi fully deterministic

Summary

Introduction

Sources of entangled electromagnetic radiation are a cornerstone in quantum information processing and offer unique opportunities for the study of quantum many-body physics in a controlled experimental setting. A generic protocol to generate entangled states as a train of sequentially emitted photons was proposed by Schön et al.[15] and is based on a long-lived auxiliary quantum system A, which sequentially interacts with an emitter qubit via a controllable coupling (see Fig. 1a).

Results

Conclusion