Andreas Lenhard

Efficient frequency downconversion at the single photon level from the red spectral range to the telecommunications C-band

We report on single photon frequency downconversion from the red part of the spectrum (738 nm) to the telecommunications C-band. By mixing attenuated laser pulses with an average photon number per pulse < 1 with a strong continuous light field at 1403 nm in a periodically poled Zn:LiNbO3 ridge waveguide an internal conversion efficiency of ∼ 73% is achieved. We further investigate the noise properties of the process by measuring the output spectrum. Our results indicate that by narrow spectral filtering a quantum interface should be feasible which bridges the wavelength gap between quantum emitters like color centers in diamond emitting in the red part of the spectrum and low-loss fiber-optic telecommunications wavelengths.

Telecom-heralded single-photon absorption by a single atom

We present, characterize, and apply the architecture of a photonic quantum interface between the near infrared and telecom spectral regions. A singly resonant optical parametric oscillator (OPO) operated below threshold, in combination with external filters, generates high-rate (

Coherence and entanglement preservation of frequency-converted heralded single photons

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Low-noise quantum frequency down-conversion of indistinguishable photons

) narrowband photon pairs (

Highly efficient heralded single-photon source for telecom wavelengths based on a PPLN waveguide

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High-fidelity entanglement between a trapped ion and a telecom photon via quantum frequency conversion

MHz bandwidth); the signal photons are tuned to resonance with an atomic transition in

Fabrication of ridge waveguides in LiNbO 3

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Single telecom photon heralding by wavelength multiplexing in an optical fiber

, while the idler photons are at telecom wavelength. Interface operation is demonstrated through high-rate absorption of single photons by a single trapped ion (

Lock-in detection of single photons after two-step frequency conversion.

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A novel integrated platform for quantum storage of heralded single photons

), heralded by coincident telecom photons.