Tunable polarization entangled photon-pair source in rhombohedral boron nitride

Area of Science:

• Quantum Optics
• Materials Science
• Nanotechnology

Background:

• Entangled photon-pair sources are crucial for quantum applications.
• Miniaturization is key for on-chip quantum devices.
• 2D semiconductors offer compact sources but have limitations in generation rate and purity.

Purpose of the Study:

• To investigate rhombohedral boron nitride (rBN) as an ultracompact entangled photon-pair source.
• To overcome the limitations of existing 2D semiconductor-based sources.
• To demonstrate the potential of rBN for on-chip quantum applications.

Main Methods:

• Utilized spontaneous parametric down-conversion (SPDC) in rBN.
• Measured photon-pair generation rate and coincidence-to-accidental ratio.
• Demonstrated tunable Bell state generation by rotating pump polarization.

Main Results:

• Achieved a record SPDC generation rate exceeding 120 Hz with 2D materials.
• Obtained high photon-pair purity with a coincidence-to-accidental ratio above 200.
• Demonstrated tunable Bell state generation with up to 0.93 fidelity.

Conclusions:

• rBN is a highly promising material for ultracompact entangled photon-pair sources.
• The achieved performance surpasses current 2D material-based sources.
• rBN is an ideal candidate for integrated quantum devices and on-chip quantum technologies.