Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 37: Poster III

Q 37.55: Poster

Wednesday, March 13, 2024, 17:00–19:00, Tent B

Characterization of second order noise processes in waveguide-based quantum frequency converters — •Ann-Kathrin Müller, Markus Struckmann, Florian Elsen, and Constantin Leon Häfner — Chair for Laser Technology, RWTH Aachen University

Quantum frequency converters (QFCs) are photonic interfaces that convert the photons emitted by qubits to the low-transmission-loss telecom bands for fiber-based quantum communication. They can be realized using difference-frequency-generation (DFG) with a strong laser field in periodically poled nonlinear materials, e.g. in a waveguide.

The aim is to maximize conversion efficiency whilst minimizing noise generation. Long-wavelength-pumped QFCs in which the strong light field is the lowest frequency component in the DFG process are theoretically considered quasi-noise-free.

However, during this work, noise characterization of a long-wavelength-pumped QFC from 856.7 nm to 1527.7 nm identified second harmonic generation (SHG) of the strong laser field with subsequent spontaneous parametric downconversion as a prominent noise source. Specifically, SHG-power in the milliwatt-regime was measured, showing the relevance of two-staged effects to noise in long-wavelength-pumped QFCs. This study advances the understanding of noise generation in QFCs, offering insights into the implications for QFC design and critical considerations for optimizing quantum networks.

Keywords: Quantum frequency converter; Noise; Quantum communication; Heterogeneous quantum network; Fiber network