V. Krutyanskiy, M. R. Meraner, J. Schupp, B. P. Lanyon Polarisation-preserving photon frequency conversion from a trapped-ion-compatible wavelength to the telecom C-band,
Appl. Phys. B Las. Opt. 123 228 (2017-09-30),
http://dx.doi.org/10.1007/s00340-017-6806-8 doi:10.1007/s00340-017-6806-8 (ID: 719939)
We demonstrate polarisation-preserving frequency conversion of single-photon-level light at 854 nm, resonant with a trapped-ion transition and qubit, to the 1550-nm telecom C band. A total photon in / fiber-coupled photon out efficiency of ∼30% is achieved, for a free-running photon noise rate of ∼60 Hz. This performance would enable telecom conversion of 854 nm polarisation qubits, produced in existing trapped-ion systems, with a signal-to-noise ratio greater than 1. In combination with near-future trapped-ion systems, our converter would enable the observation of entanglement between an ion and a photon that has travelled more than 100 km in optical fiber: three orders of magnitude further than the state-of-the-art.