A two-way photonic interface for linking Sr+ transition at 422 nm to the telecommunications C-band

Thomas A. Wright, Robert J.A. Francis-Jones, Corin B.E. Gawith, Jonas N. Becker, Patrick M. Ledingham, Peter G.R. Smith, Joshua Nunn, Peter J. Mosley, Benjamin Brecht, Ian A. Walmsley

Abstract

We report a single-stage bi-directional interface capable of linking Sr+ trapped ion qubits in a long-distance quantum network. Our interface converts photons between the Sr+ emission wavelength at 422 nm and the telecoms C-band to enable low-loss transmission over optical fiber. We have achieved both up- and down-conversion at the single photon level with efficiencies of 9.4% and 1.1% respectively. Furthermore we demonstrate noise levels that are low enough to allow for genuine quantum operation in the future.