Control of the cavity reflectivity using a single quantum dot spin

We experimentally realize a solid-state spin-photon transistor using a quantum dot strongly coupled to a photonic crystal cavity. We are able to control the light polarization through manipulation of the quantum dot spin states. The spinphoton transistor is crucial for realizing a quantum logic gate or generating hybrid entanglement between a quantum dot spin and a photon. Our results represent an important step towards semiconductor based quantum logic devices and onchip quantum networks.