Coherent frequency bridge between visible and telecommunications band for vortex light

Area of Science:

• Quantum optics
• Quantum communication technologies

Background:

• High-dimensional quantum communication networks (HDCNs) utilize vortex photons to encode quantum states.
• Interfaces connecting different wavelengths are crucial for building robust HDCNs.

Purpose of the Study:

• To construct a coherent orbital angular momentum (OAM) frequency bridge for interfacing quantum systems operating at different wavelengths.
• To enable the transmission of high-dimensional quantum states across visible and infrared spectra.

Main Methods:

• Difference frequency conversion in a nonlinear bulk crystal.
• Utilizing a single resonant cavity for efficient OAM frequency conversion.
• Quantum state tomography to verify the fidelity of down-converted OAM states.

Main Results:

• Achieved maximum quantum conversion efficiencies of 36% (topological charge 0), 15% (topological charge 1), and 7.8% (topological charge 2) from visible to infrared.
• Obtained an average fidelity of 96.51% for down-converted infrared OAM states (topological charge 1).
• Demonstrated conservation of OAM through interference pattern analysis.

Conclusions:

• The developed coherent OAM frequency-down conversion bridge serves as a foundational interface for HDCNs.
• This technology facilitates the integration of quantum systems operating at disparate spectral bands.
• The OAM conservation confirms the integrity of quantum information transfer across wavelengths.