Realizing a sensitive photon-number-dependent phase shift on a light beam is required both in classical and quantum photonics. It may lead to new applications for classical and quantum photonics machine learning or pave the way for realizing photon-photon gate operations. Non-linear phase-shifts require efficient light-matter interaction, and recently quantum dots coupled to nanophotonic devices have enabled near-deterministic single-photon coupling. We experimentally realize an optical phase shift of 0.19π±0.03 radians (≈34 degrees) using a weak coherent state interacting with a single quantum dot in a planar nanophotonic waveguide. The phase shift is probed by interferometric measurements of the light scattered from the quantum dot in the waveguide. The nonlinear process is sensitive at the single-photon level and can be made compatible with scalable photonic integrated circuitry. The work may open new prospects for realizing high-efficiency optical switching or be applied for proof-of-concept quantum machine learning or quantum simulation demonstrations.
@article{arxiv.2305.06839,
title = {Direct observation of non-linear optical phase shift induced by a single quantum emitter in a waveguide},
author = {Mathias J. R. Staunstrup and Alexey Tiranov and Ying Wang and Sven Scholz and Andreas D. Wieck and Arne Ludwig and Leonardo Midolo and Nir Rotenberg and Peter Lodahl and Hanna Le Jeannic},
journal= {arXiv preprint arXiv:2305.06839},
year = {2023}
}