Quantum Frequency Conversion of $\mu s$-long Photons from the Visible to the Telecom-C-Band

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 $\mu s$ with a device efficiency of about 25% and a signal-to-noise ratio >460 for 10 $\mu s$-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.

7 pages, 6 figures

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• The Quantum Internet
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• Tunable ion-photon entanglement in an optical cavity
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• Efficient polarisation-preserving frequency conversion from a trapped-ion-compatible wavelength to the telecom C band

Cited by in corpus (1)

• Fiber-integrated Quantum Frequency Conversion for Long-distance Quantum Networking