Quantum 2025 – scientific programme

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MON: Monday Contributed Sessions

MON 1: QIP Implementations: Photons I

MON 1.4: Talk

Monday, September 8, 2025, 15:00–15:15, ZHG001

Low-noise cascaded frequency conversion of 637.2 nm light to the telecommunication C-band in a single-waveguide device — Fabrice von Chamier, Joscha Hanel, Chris Müller, Wanrong Li, •Roger Kögler, and Oliver Benson — Humboldt-Universität zu Berlin, Institut für Physik, Newtonstraße 15, 12489, Berlin, Germany

Quantum devices and optical states often operate at disparate frequencies, making frequency conversion essential for connecting nodes in quantum networks. Here, we demonstrate a two-stage frequency conversion using an integrated device, successfully converting 637.2 nm photons emitted by nitrogen-vacancy centers in diamond into telecom wavelengths. Our system achieves low internal (external) noise spectral densities of 2.4 ± 0.8 (16 ± 5) cps/GHz, owing to the cascaded architecture, which mitigates excess noise typically introduced by spontaneous parametric down-conversion from the strong pump field.

The device is based on a periodically poled lithium niobate waveguide featuring two distinct poling sections. Remarkably, it also exhibits a phase-matched interaction between thermally generated photons and the pump field, which we investigate in detail. Additionally, we demonstrate tunable frequency conversion across the C-band by thermally controlling the phase-matching conditions of each stage. This enables wavelength targeting in the range of 1559.0 nm to 1564.9 nm, with external (internal) conversion efficiencies reaching 3.0 ± 0.1 % (20.5 ± 0.8%).

Keywords: Frequency Conversion; Nitrogen-Vacancy Center; Quantum Networks