Electrically pumped ultrabright entangled photons on chip

This paper presents an electrically pumped polarization-entangled photon source (EPS) on a hybrid thin-film lithium niobate (TFLN) platform, addressing the challenges of scalability and performance in chip-scale quantum devices. The device integrates a distributed feedback (DFB) laser with a TFLN chip, which contains periodically poled lithium niobate (PPLN) waveguides, a beam splitter, and a polarization rotator combiner. It demonstrates an efficient polarization-EPS with a bandwidth of 73 nm and an entangled pair generation rate (PGR) of 4.5×10^10 pairs/s/mW. The generated photon pairs exhibit high fidelity, with Bell-state fidelities above 96%.

Key findings include:

1. Hybrid Integration: The DFB laser emits horizontally polarized light at approximately 780 nm, which is coupled into the TFLN chip. This integration enables efficient pump power injection, achieving a side-mode suppression ratio over 40 dB and polarization extinction ratios greater than 20 dB.

2. Performance Metrics: The device achieves a high PGR of 4.5×10^10 pairs/s/mW and a broad operational bandwidth of 73 nm. These results show a significant improvement in both brightness and bandwidth over previous EPS sources.

3. Polarization Entanglement: The polarization entanglement of the photon pairs is characterized with high fidelity across different frequency modes, exceeding 96%. The experimental setup uses a polarizer to separate signal and idler photons, which are then analyzed for polarization correlation.

4. Broadband Capability: The system operates over a broad wavelength range, with the signal and idler photons exhibiting bandwidths of 73 nm and 80 nm, respectively. This broad spectrum is essential for multi-channel quantum applications.

5. Applications: The integrated EPS is poised to contribute to a wide range of quantum technologies, including high-speed quantum key distribution (QKD), satellite-based quantum communication, and entanglement-based quantum metrology.

In conclusion, this work demonstrates a significant advancement in on-chip polarization-entangled photon generation, providing a compact, efficient, and scalable solution for quantum communication and quantum information processing. The system's high performance and broad bandwidth make it suitable for multi-channel and high-dimensional quantum applications.