Coherent Manipulation of a Quantum Dot with Few Photons in a Low‐Reflectivity Micropillar Cavity

ABSTRACT Bidirectional coherent control between photonic and matter qubits in solid‐state quantum networks demand a tailored photon‐emitter interface that can operate at the few‐photon level. Cavity‐coupled quantum dots with high input coupling efficiency provides a viable path toward such interface. However, reflection from the bare cavity can contaminate, or even overwhelm, the desired output photons that have interacted with the emitter. To overcome this problem, we implement a low‐reflectivity ( 1%) quantum dot‐micropillar cavity system with 97% input coupling efficiency. We achieve an optical nonlinearity threshold of 5.6 incident photons per pulse while maintaining high antibunching fidelity ( 0.2), measured at a pulse duration of twice the quantum dot exciton lifetime. Furthermore, we observe quantum dot transition inversion at 9 photons when the pulse duration is reduced to roughly match the quantum dot lifetime. This highly efficient photon‐emitter interface paves the way for key quantum photonic resources and functionalities.