标题： 确定性增强超纯钻石中氮-空位中心的相干光子产生 显示英文标题

标题： Deterministic enhancement of coherent photon generation from a nitrogen-vacancy center in ultrapure diamond

摘要： 金刚石中的氮-空位（NV）中心具有光学可寻址且高相干性的自旋。然而，即使在高质量的单晶材料中，NV中心也只是一个非常差的单光子源：从高折射率的金刚石中提取效率低下，相干光子的发射仅占总发射量的百分之几，并且衰减时间较长。原则上，这三个问题都可以通过共振微腔解决。但实际上，实现这一概念被证明是困难的：光子工程依赖于纳米加工，但众所周知，处理金刚石时很难不损害NV中心的质量。我们在这里提出了一种微腔方案，它使用了经过最少加工的金刚石，从而保留了起始材料的高质量，并提供了一个可调谐的微腔平台。我们展示了当调节腔频率和节点位置时，多个单独的NV中心的寿命发生了明显变化，这是一种帕尔默效应。总体帕尔默因子$F_{\rm P}=2.0$转化为零声子线（ZPL）的帕尔默因子$F_{\rm P}^{\rm ZPL}\sim30$，以及ZPL发射概率从$\sim 3 \%$增加到$\sim 46 \%$。通过以确定性的方式对NV的光学性质做出变革性改进，这些结果为大幅提升自旋-光子和自旋-自旋纠缠速率铺平了道路。 显示英文摘要

摘要： The nitrogen-vacancy (NV) center in diamond has an optically addressable, highly coherent spin. However, an NV center even in high quality single-crystalline material is a very poor source of single photons: extraction out of the high-index diamond is inefficient, the emission of coherent photons represents just a few per cent of the total emission, and the decay time is large. In principle, all three problems can be addressed with a resonant microcavity. In practice, it has proved difficult to implement this concept: photonic engineering hinges on nano-fabrication yet it is notoriously difficult to process diamond without degrading the NV centers. We present here a microcavity scheme which uses minimally processed diamond, thereby preserving the high quality of the starting material, and a tunable microcavity platform. We demonstrate a clear change in the lifetime for multiple individual NV centers on tuning both the cavity frequency and anti-node position, a Purcell effect. The overall Purcell factor $F_{\rm P}=2.0$ translates to a Purcell factor for the zero phonon line (ZPL) of $F_{\rm P}^{\rm ZPL}\sim30$ and an increase in the ZPL emission probability from $\sim 3 \%$ to $\sim 46 \%$. By making a step-change in the NV's optical properties in a deterministic way, these results pave the way for much enhanced spin-photon and spin-spin entanglement rates.