Efficient Polarization-Entangled Photon-Pair Generation by a Fiber-In-Line van der Waals Material

Area of Science:

• Quantum Optics and Photonics
• Materials Science
• Condensed Matter Physics

Background:

• Van der Waals (vdW) materials exhibit significant optical nonlinearity, enabling advancements in nonlinear photonics.
• Integrating vdW materials into fiber-optic platforms is crucial for quantum systems but faces challenges in telecom-band applications.
• Developing efficient in-line photon-pair sources is essential for quantum networking and computing.

Purpose of the Study:

• To demonstrate telecom-band photon-pair generation using a fiber-integrated ferroelectric vdW crystal.
• To investigate the nonlinear optical properties of SnP2S6 for photonic device applications.
• To establish a scalable platform for functionalized quantum photonic systems.

Main Methods:

• Fabrication of a fiber-integrated device incorporating a few-micrometer-thick SnP2S6 film.
• Utilizing spontaneous parametric down-conversion for photon-pair generation.
• Characterization of nonlinear conversion efficiency, coincidence rates, coincidence-to-accidental ratio, and quantum state tomography for polarization entanglement.

Main Results:

• Achieved a nonlinear conversion efficiency of 0.07% in the SnP2S6 film.
• Generated high-quality photon pairs at telecom wavelengths with a detected coincidence rate of 102 counts/s.
• Demonstrated polarization-entangled photon pairs with high fidelities (0.97) and concurrences (0.95).

Conclusions:

• The fiber-integrated SnP2S6 device offers a robust and scalable platform for quantum photonics.
• The study highlights the potential of ferroelectric vdW materials for next-generation nonlinear photonic devices.
• This work paves the way for low-loss quantum photonic systems for networking, sensing, and computing.