The spin of an electron is a promising memory state and qubit. Connecting spin states that are spatially far apart will enable quantum nodes and quantum networks based on the electron spin. Towards this goal, an integrated spin–photon interface would be a major leap forward as it combines the memory capability of a single spin with the efficient transfer of information by photons. Here, we demonstrate such an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared in the ground state with a fidelity of up to 96%. Subsequently, the system is used to implement a single-spin photonic switch, in which the spin state of the electron directs the flow of photons through the waveguide. The spin–photon interface may enable on-chip photon–photon gates, single-photon transistors and the efficient generation of a photonic cluster state.

电子的自旋是一种有前途的记忆状态和量子位。连接空间上相距很远的自旋态将使基于电子自旋的量子节点和量子网络成为可能。为了实现这一目标，集成的自旋-光子接口将是一个重大飞跃，因为它将单次自旋的存储能力与光子的有效信息传输相结合。在这里，我们演示了量子点中的电子自旋与纳米光子波导中的光子之间的这种高效且光学可编程的接口。可以以高达96％的保真度确定地在基态中准备自旋。随后，该系统用于实现单旋光子开关，其中电子的自旋态将光子流引导通过波导。