This paper experimentally demonstrates an optical phase shift of 0.19 ± 0.03 radians (≈34 degrees) using a weak coherent state interacting with a single quantum dot in a planar nanophotonic waveguide. The phase shift, probed interferometrically, is nonlinear in power, saturates at the single-photon level, and is compatible with scalable photonic integrated circuitry. This work opens prospects for high-efficiency optical switching and applications in quantum machine learning and quantum simulation.

Mathias J. R. Staunstrup, Alexey Tiranov, Ying Wang, Sven Scholz, Andreas D. Wieck, Arne Ludwig, Leonardo Midolo, Nir Rotenberg, Peter Lodahl, Hanna Le Jeannic