The nitrogen-vacancy center in diamond is an attractive resource for the generation of remote entangled states owing to its optically addressable and long-lived electronic spin. However, its low native fraction of coherent photon emission, ~3%, undermines the achievable spin-photon entanglement rates. Here, we couple a nitrogen-vacancy center with a narrow extrinsically-broadened linewidth (159 MHz), hosted in a micron-thin membrane, to an open microcavity. The resulting Purcell factor of ~1.8 increases the zero-phonon line fraction to over 44%. Operation in the Purcell regime, together with an efficient collection of the zero-phonon-line photons, allows resonance fluorescence to be detected for the first time without any temporal filtering. We achieve a >10 signal-to-laser background ratio. This selective enhancement of the center’s zero-phonon transitions could increase spin-spin entanglement success probabilities beyond an order of magnitude compared to state-of-the-art implementations, and enable powerful quantum optics techniques such as wave-packet shaping or all-optical spin manipulation.

金刚石中的氮空位中心由于其光学可寻址且寿命长的电子自旋，是产生远程纠缠态的有吸引力的资源。然而，其相干光子发射的低天然分数 ~3%，破坏了可实现的自旋光子纠缠速率。在这里，我们将一个氮空位中心与一个狭窄的外部加宽线宽 （159 MHz） 耦合到一个开放的微腔中，该中心位于微米薄膜中。得到的 Purcell 因子 ~1.8 将零声子线分数增加到 44% 以上。在 Purcell 模式下运行，再加上零声子线光子的高效收集，可以首次检测到共振荧光，而无需任何时间过滤。我们实现了 >10 信令与激光背景比。与最先进的实现相比，该中心的零声子跃迁的这种选择性增强可以将自旋-自旋纠缠成功概率提高一个数量级以上，并实现强大的量子光学技术，例如波包整形或全光自旋操纵。