Realisation of a Coherent and Efficient One-Dimensional Atom

A quantum emitter interacting with photons in a single optical-mode constitutes a one-dimensional atom. A coherent and efficiently coupled one-dimensional atom provides a large nonlinearity, enabling photonic quantum gates. Achieving a high coupling efficiency (-factor) and low dephasing is challenging. Here, we use a semiconductor quantum dot in an open microcavity as an implementation of a one-dimensional atom. With a weak laser input, we achieve an extinction of 99. 2\% in transmission and a concomitant bunching in the photon statistics of g^ (2) (0) = 587, showcasing the reflection of the single-photon component and the transmission of the multi-photon components of the coherent input. The tunable nature of the microcavity allows to be adjusted and gives control over the photon statistics -- from strong bunching to anti-bunching -- and the phase of the transmitted photons. We obtain excellent agreement between experiment and theory by going beyond the single-mode Jaynes-Cummings model. Our results pave the way towards the creation of exotic photonic states and two-photon phase gates.