Counter-propagating entangled photon pairs from monolayer GaSe

Area of Science:

• Quantum optics
• Materials science
• Nanotechnology

Background:

• Non-phase-matched spontaneous parametric down-conversion (SPDC) in thin materials offers enhanced quantum information capacity.
• Previous studies faced challenges in observing photon-pair emission from monolayers.
• Thin materials are promising for quantum computing, communication, and imaging.

Purpose of the Study:

• To theoretically model and experimentally validate SPDC emission from a monolayer GaSe film.
• To demonstrate two-photon quantum correlations and high-fidelity Bell states.
• To explore the potential of atomically thin materials for scalable quantum state generation.

Main Methods:

• Theoretical modeling of SPDC emission across the full angular space.
• Experimental validation using co- and counter-propagating photon pair measurements.
• Characterization of quantum correlations in the telecom C-band.

Main Results:

• Spatially symmetric, broadband SPDC emission was observed, matching theoretical predictions.
• Two-photon quantum correlations were demonstrated from a monolayer SPDC source.
• High-fidelity Bell states were generated in the counter-propagating configuration.

Conclusions:

• Atomically thin, non-phase-matched SPDC is a viable platform for quantum information.
• The study confirmed SPDC emission characteristics in the subwavelength regime.
• Counter-propagating SPDC in thin films offers a scalable and integrable approach for quantum state generation.