Wide-band quantum interface for visible-to-telecommunication wavelength conversion

Area of Science:

• Quantum Information Science
• Photonics
• Quantum Communication

Background:

• Visible photons are widely used in quantum information tasks, but near-infrared photons are needed for long-distance quantum communication.
• Bridging the wavelength gap between visible and telecommunication bands is essential for integrating current quantum technologies with future long-distance networks.
• Atomic quantum memories and other sources generate visible photons, necessitating wavelength conversion.

Purpose of the Study:

• To demonstrate a quantum interface for optical frequency down-conversion from visible to telecommunication wavelengths.
• To develop a high-speed frequency conversion interface using a nonlinear crystal.
• To confirm that the quantum states, specifically entanglement, are preserved during the down-conversion process.

Main Methods:

• Utilized a nonlinear crystal for optical frequency down-conversion.
• Converted a picosecond visible photon at 780 nm to a 1,522 nm photon.
• Employed techniques to verify the preservation of quantum entanglement between the down-converted photon and its entangled partner.

Main Results:

• Successfully demonstrated frequency down-conversion from 780 nm (visible) to 1,522 nm (telecommunication band).
• Achieved conversion of picosecond-duration photons, indicating potential for high-speed operation.
• Confirmed that the quantum entanglement was retained after the frequency down-conversion process.

Conclusions:

• The developed quantum interface effectively bridges the wavelength gap between visible and telecommunication bands.
• The nonlinear crystal-based approach offers a promising route for high-speed quantum frequency conversion.
• Preservation of entanglement is a critical step towards realizing robust quantum communication networks utilizing diverse photon sources.