Quantum frequency conversion of quantum memory compatible photons to telecommunication wavelengths

Area of Science:

• Quantum Optics
• Quantum Information Science
• Nonlinear Optics

Background:

• Atomic quantum memories operate at specific wavelengths, limiting integration with telecommunication systems.
• Efficient frequency conversion is crucial for interfacing quantum memories with optical fibers.

Purpose of the Study:

• To demonstrate quantum frequency conversion of weak light pulses compatible with atomic quantum memories.
• To convert pulses from 780 nm to telecommunication wavelengths (1552 nm).

Main Methods:

• Utilized a periodically poled lithium niobate (PPLN) nonlinear waveguide.
• Converted weak coherent states at the single-photon level.
• Measured waveguide internal and external conversion efficiencies.
• Analyzed signal-to-noise ratio (SNR) and pump-induced noise.

Main Results:

• Achieved maximal internal conversion efficiency of 0.41 (external 0.25).
• Demonstrated SNR sufficient for input photon numbers below 1.
• Showed pump-induced noise is proportional to spectral bandwidth, indicating potential for improvement with narrower filtering.
• Successfully converted a time-bin qubit, preserving its quantum state.

Conclusions:

• The developed quantum frequency converter is compatible with atomic quantum memories and telecommunication wavelengths.
• The device operates effectively in the quantum regime, preserving qubit fidelity.
• Optimizing spectral bandwidth offers a pathway to significantly enhance SNR for future quantum communication applications.