Quantum 2025 – scientific programme

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THU: Thursday Contributed Sessions

THU 13: Poster Session: Applications

THU 13.29: Poster

Thursday, September 11, 2025, 16:30–18:30, ZHG Foyer 1. OG

Setup and calibration of a single-photon spectrometer — •Jannis Sode, David Lindler, Marlon Schäfer, Tobias Bauer, Akriti Raj, and Christoph Becher — Universität des Saarlandes, Fachrichtung Physik, Campus E2 6, 66123 Saarbrücken

Fiber-based quantum networks consist of spin-photon interfaced quantum memory nodes utilizing flying qubits with wavelengths in the low-loss telecom bands. These photons are either directly generated via optical transitions or transducted using quantum frequency conversion. This enables communication and transfer of quantum states via preexisting optical fiber infrastructure. Due to the small signal level of the transmitted quantum states of light, it is mandatory to explore and control the noise sources in the transmission channels.
To this end, an exact spectral analysis of signals on the single-photon level is necessary to determine the spectral noise distribution. However, commercially available spectrometers typically have a small detection efficiency at infrared wavelengths.
In this contribution, we present the setup of a spectrometer able to measure single-photon signals in the telecom wavelength range (1500-1600 nm) using superconducting nanowire single photon detectors with high detection efficiency. We discuss the overall efficiency as well as the accuracy of the spectrometer. To demonstrate its performance we resolve the spectral distribution of non-linear optical processes at the single-photon level, in particular spontaneous parametric down conversion and pump-induced noise in quantum frequency conversion.

Keywords: quantum communication; single-photon detectors; quantum networks