Observation of Genuine Tripartite Non-Gaussian Entanglement from a Superconducting Three-Photon Spontaneous...

Area of Science:

• Quantum Optics
• Quantum Information Science
• Superconducting Circuits

Background:

• Spontaneous parametric down-conversion (SPDC) traditionally generates entangled photon pairs.
• Circuit quantum electrodynamics enables novel nonlinear processes like three-photon SPDC (3P-SPDC).
• Confirming tripartite entanglement from 3P-SPDC sources is crucial for quantum applications.

Purpose of the Study:

• To experimentally demonstrate genuine tripartite non-Gaussian entanglement from a 3P-SPDC source.
• To characterize the observed entanglement using an entanglement witness.
• To investigate the influence of photon mode definition on entanglement measurements.

Main Methods:

• Utilized a 3P-SPDC source based on a superconducting parametric cavity coupled to a transmission line.
• Employed an entanglement witness derived from three-mode correlation functions to quantify tripartite entanglement.
• Analyzed the scaling of the entanglement witness and compared it with theoretical predictions.

Main Results:

• Observed genuine tripartite non-Gaussian entanglement in the steady-state output of the 3P-SPDC source.
• Achieved a maximum violation of the entanglement witness bound by 15 standard deviations.
• Found strong agreement between experimental results and analytical predictions for entanglement witness scaling.

Conclusions:

• Successfully demonstrated and confirmed tripartite non-Gaussian entanglement from a 3P-SPDC source.
• The developed entanglement witness is effective for detecting and quantifying multipartite entanglement.
• The study provides a foundational resource for advancing quantum information processing and quantum communication.