Our system, consisting of a trapped ion in the focus of an optical cavity, achieves close to the optimal compromise between the probability of a photon being emitted into the cavity mode and exiting through the output mirror. Furthermore, the achieved performance is shown to saturate recently-developed theoretical limits, set only by the cavity and emitter parameters, allowing the paths to future efficiency improvements to be clearly identified. The comparison between measured probabilities and theoretical limits is relevant for quantum emitters beyond trapped ions, in particular, for the design of future systems optimising photon collection from, and absorption in, quantum matter.
An intriguing outlook is to combine the multi-qubit quantum-logic capabilities of the trapped-ion platform with the high-efficiency photon generation achieved in this work, to generate new many-body light-matter quantum states with widespread application. Indeed, as a first step in that direction we demonstrate here the detection of up to 15 sequential photons.
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