Robust and bright polarization-entangled photon sources exploiting non-critical phase matching without periodic poling

Area of Science:

• Quantum optics
• Photonics
• Quantum information science

Background:

• Entangled photon sources are crucial for quantum computation, communication, and metrology.
• Periodically poled (PP) crystals are standard for generating photons via quasi-phase matching, but fabrication is challenging and limits crystal size.
• Existing methods face limitations in brightness and scalability due to fabrication constraints.

Purpose of the Study:

• To develop a robust and bright polarization-entangled photon source.
• To overcome the limitations of periodically poled crystals in generating entangled photons.
• To enable scalable and practical photonic quantum information applications.

Main Methods:

• Utilized non-critical phase matching (NCPM) in a bulk KTP crystal within a Sagnac interferometer.
• Avoided the need for periodic poling, allowing for larger crystal cross-sections.
• Characterized the generated entangled photon states for purity, concurrence, and fidelity.

Main Results:

• Achieved a robust and bright polarization-entangled photon source.
• Demonstrated a brightness of 25.1 kHz/mW at 1079 nm.
• Obtained purity, concurrence, and fidelity values close to 0.99 for the four Bell states.
• NCPM offers theoretical brightness enhancement and tolerance to environmental variations.

Conclusions:

• The developed NCPM scheme provides a significant advancement for entangled photon generation.
• This method offers a practical and scalable alternative to traditional quasi-phase matching techniques.
• The robust source is a key building block for future photonic quantum information systems.