Solid-state ensemble of highly entangled photon sources at rubidium atomic transitions

Area of Science:

• Quantum photonics
• Solid-state physics
• Materials science

Background:

• Semiconductor quantum dots, specifically InAs/GaAs, are explored for generating polarization-entangled photon pairs.
• Current Stranski-Krastanov grown quantum dots face challenges including low yield, limited entanglement degree, and broad wavelength distribution.
• These limitations hinder the development of practical quantum photonic devices.

Purpose of the Study:

• To investigate an emerging GaAs/AlGaAs quantum dot system for scalable, high-performance entangled photon generation.
• To demonstrate wafer-scale production of polarization-entangled photon emitters without post-growth tuning.
• To assess the purity, entanglement degree, and wavelength distribution of photons emitted from these new quantum dots.

Main Methods:

• Utilizing droplet etching and nanohole infilling for GaAs/AlGaAs quantum dot fabrication.
• Employing pulsed resonant two-photon excitation for photon generation.
• Characterizing the generated photon pairs for purity, entanglement fidelity, and spectral properties.

Main Results:

• A large ensemble of polarization-entangled photon emitters was successfully produced on a wafer.
• All measured quantum dots exhibited ultra-high purity single entangled photon pair emission.
• The quantum dots demonstrated a high degree of entanglement and an ultra-narrow wavelength distribution, matching rubidium transitions.

Conclusions:

• GaAs/AlGaAs quantum dots grown by droplet etching and nanohole infilling present a significant advancement over traditional InAs/GaAs systems.
• This novel material system enables efficient, high-quality entangled photon generation at the wafer scale.
• These findings position the GaAs/AlGaAs quantum dots as a promising candidate for solid-state quantum repeaters and other quantum photonic elements.