Four-Photon Greenberger-Horne-Zeilinger Entanglement via Collective Two-Photon Coherence in Doppler-Broadened Atoms

Bright, entangled multiphoton sources based on atom-photon interactions are an essential requirement in the realization of several quantum information and quantum computation schemes based on photonic quantum systems. Here, a four-photon polarization-entangled Greenberger-Horne-Zeilinger (GHZ) state obtained from Doppler-broadened atomic ensembles of Rb-87 atoms is experimentally demonstrated. Owing to collective two-photon coherence in the Doppler-broadened cascade-type atomic system, the setup enables the generation of robust four-photon GHZ states with a fidelity of 82.1% and a measured four-photon average coincidence rate of 0.58 s(-1). It is believed that the generation of such bright and stable multiphoton GHZ states from atomic media is an important step toward realizing photonic quantum computation and practical quantum networks based on atom-photon interactions.

Automated summary

This experiment demonstrates the generation of a four-photon polarization-entangled GHZ state from Doppler-broadened atomic ensembles of Rb-87 atoms, achieving a high fidelity of 82.1% and stable performance, marking a significant step towards practical quantum networks and photonic quantum computation based on atom-photon interactions.