Compact polarization-entangled photon-pair source based on a dual-periodically-poled Ti:LiNbO₃ waveguide

Area of Science:

• Quantum optics
• Integrated photonics
• Materials science

Background:

• Development of reliable and compact sources for entangled photon pairs is crucial for advancing quantum communication and computation.
• Existing sources often face challenges with stability, brightness, and integration into existing network infrastructure.

Purpose of the Study:

• To experimentally realize a compact and stable source of nondegenerate polarization-entangled photon pairs.
• To ensure compatibility with telecommunication windows and fiber quantum networks.

Main Methods:

• Utilized a dual-periodically-poled titanium-indium-lithium-niobate (Ti:LiNbO3) waveguide.
• Employed two concurrent quasiphase-matching spontaneous parametric down-conversion (SPDC) processes pumped by a single laser.
• Performed quantum state tomography to characterize the generated entangled states.

Main Results:

• Achieved a high brightness of 1.22 × 10^7 pairs/(s×mW×nm).
• Demonstrated high entanglement fidelity of 0.945 ± 0.003.
• Confirmed quantum correlations via a violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality with S = 2.75 ± 0.03.

Conclusions:

• The dual-periodically-poled waveguide approach offers a compact and stable solution for generating polarization-entangled photons.
• The source's performance metrics are suitable for practical implementation in fiber-based quantum networks.
• This work paves the way for scalable quantum information processing and secure communication systems.