Entangled photon generation in two-period quasi-phase-matched parametric down-conversion.

Area of Science:

• Quantum optics
• Nonlinear optics
• Photonics

Background:

• Entangled photon pairs are crucial for quantum communication and computation.
• Spontaneous parametric down-conversion (SPDC) is a common method for generating entangled photons.
• Generating entangled photons at telecommunication wavelengths is essential for fiber-optic quantum networks.

Purpose of the Study:

• To propose and demonstrate a simple, deterministic scheme for generating polarization-entangled photon pairs.
• To achieve entanglement at telecommunication wavelengths (1506 nm and 1594 nm).
• To utilize type-II quasi-phase-matched spontaneous parametric down-conversion (QPM-SPDC) with two poling periods.

Main Methods:

• Fabrication of a lithium niobate (LiNbO3) crystal with two distinct poling periods.
• Utilizing type-II QPM-SPDC to generate photon pairs.
• Characterization of the two-photon polarization state using quantum state tomography.

Main Results:

• Successful generation of polarization-entangled photon pairs at 1506 nm and 1594 nm.
• Demonstration of a simple and deterministic entanglement generation scheme.
• Confirmation of a highly entangled two-photon polarization state via state tomography.

Conclusions:

• The proposed QPM-SPDC scheme is effective for generating high-quality entangled photon pairs at telecommunication wavelengths.
• The fabricated LiNbO3 crystal with dual poling periods enables simultaneous entanglement generation at two distinct wavelengths.
• This work contributes to the advancement of quantum communication technologies by providing a practical method for generating essential quantum resources.