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 (>2.5×10⁶0.222222em0exs^-1) narrowband photon pairs (~7 MHz bandwidth); the signal photons are tuned to resonance with an atomic transition in Ca⁺, while the idler photons are at telecom wavelength. Interface operation is demonstrated through high-rate absorption of single photons by a single trapped ion (~6700.222222em0exs^-1), heralded by coincident telecom photons.