Waveguide-QED in a nanowire quantum dot system

A single two-level system coupled strongly to a one-dimensional optical waveguide mode has been a challenge in realizing a true waveguide-QED system. Such a system can be realized with a single quantum dot (QD) grown on the axis of a nanowire (NW) with a single optical waveguide mode. In this study, we investigate light injection into a tapered InP NW with an InAsP QD using k-space extinction microscopy. Numerical simulations estimate that > 80% extinction of reflected laser light under mode matching conditions corresponds to ≈ 90% in-coupling of the input light into the fundamental waveguide mode of the NW. We experimentally verify this claim of near-ideal mode matching and reflect light from the quantum dot under the Heitler regime. We observe that the reflected light has the coherence of the laser with strong antibunching (g2(0) < 0.1). Mode-matching the input laser and the reflected signal removes the requirement for any additional filtering techniques that were necessary in previous works to supress the laser light that does not interact with the QD. Our work demonstrates a true realization of a single two-level system coupled to a one-dimensional electromagnetic mode.