Time-resolved certification of frequency-bin entanglement over multi-mode channels

Area of Science:

• Quantum Information Science
• Quantum Communication Technologies
• Integrated Photonics

Background:

• On-chip frequency-bin entangled photon sources offer scalable quantum communication platforms.
• Current analysis methods for entangled photons are active, lossy, and limit scalability and multi-mode compatibility.

Purpose of the Study:

• To demonstrate a novel, passive technique for processing frequency-encoded photons using linear interferometry and time-resolved detection.
• To enable arbitrary projective measurements on single- and multi-mode frequency-bin entangled states.
• To establish a resource-efficient and scalable approach for quantum communication over free-space and satellite links.

Main Methods:

• Utilized frequency-bin entangled photons from a high-brightness multi-resonator source.
• Employed linear interferometry and time-resolved detection for photon processing.
• Performed joint temporal intensity measurements and quantum state tomography.

Main Results:

• Demonstrated arbitrary projective measurements on single- and multi-mode channels.
• Certified entanglement by violating the Clauser-Horne-Shimony-Holt (CHSH) inequality with ∣S∣ = 2.32 ± 0.05 over multi-mode fiber.
• Achieved up to 91% state fidelity through quantum state tomography.
• Violated time-energy entropic uncertainty relations, indicating non-classical state generation.

Conclusions:

• The developed passive technique is compatible with spatially multi-mode light and suitable for free-space and satellite applications.
• This approach overcomes limitations of active components, enhancing scalability and multi-mode compatibility.
• The study paves the way for robust frequency-bin entanglement deployment in resource-constrained quantum communication systems.