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arXiv · 2412.15193

Quantum Frequency Conversion of $μs$-long Photons from the Visible to the Telecom-C-Band

Soeren Wengerowsky·Stefano Duranti·Lukas Heller·Hugues de Riedmatten
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Abstract

Quantum Frequency Conversion (QFC) is a widely used technique to interface atomic systems with the telecom band in order to facilitate propagation over longer distances in fiber. Here we demonstrate the difference-frequency conversion from 606 nm to 1552 nm of microsecond-long weak coherent pulses at the single photon level compatible with Pr$^{3+}$:Y$_2$SiO$_5\,$ quantum memories, with high-signal to noise ratio. We use a single step difference frequency generation process with a continuous-wave pump at 994 nm in a MgO:ppLN-waveguide and ultra-narrow spectral filtering down to a bandwidth of 12.5 MHz. With this setup, we achieve the conversion of weak coherent pulses of duration up to 13.6 $μs$ with a device efficiency of about 25% and a signal-to-noise ratio >460 for 10 $μs$-long pulses containing one photon on average. This signal-to-noise ratio is large enough to enable a high-fidelity conversion of qubits emitted from an emissive quantum memory based on Pr$^{3+}$:Y$_2$SiO$_5\,$ and to realize an interface with quantum processing nodes based on narrow-linewidth cavity-enhanced trapped ions.

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Soeren Wengerowsky, Stefano Duranti, Lukas Heller, Hugues de Riedmatten. 2025-02-24. Quantum Frequency Conversion of $μs$-long Photons from the Visible to the Telecom-C-Band. https://doi.org/10.1103/physrevapplied.23.024049

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