Enhanced quantum sensing with a nitrogen-vacancy centre as gateway to the electron spin of phosphorus

为了研究“金刚石中NV中心附近的磷施主的电子自旋能否用作量子传感器”这一关键科学问题，首先对几个磷掺杂样品进行了测量。掺杂浓度约为10^16原子/厘米^3。然而，与初始测量相反，在测量的NV中心附近没有来自任何缺陷/杂质的响应。对此有几种可能的解释，目前正在研究。第一，可能需要更高的磷浓度，以便有公平的机会使供体足够接近NV中心。这将通过尽可能地增加磷浓度来尝试。第二，测量方法可能不够。为了研究这一点，我们决定研究一种更“简单”（但又新）的情况：耦合两个NV中心。在QST的帮助下，我们将具有多个氮原子的分子注入到掺磷金刚石中，以使NV中心很有可能靠近在一起。我们的想法是首先尝试使用这种耦合进行量子传感，因为与两个NV中心的相互作用是可能的（如果它们的方向不同），因此与使用暗自旋相比更容易。虽然我们能够相当容易地找到具有不同取向的NV中心对，但它们要么不稳定（可能是电荷状态），要么它们的相干时间非常短（大约1微秒而不是接近1毫秒）。第三，我们研究了一种可能更合适的不同测量方法。我们将很快提交后者供出版。

In order to investigate the key scientific question, "can the electron spins of phosphorus donors nearby NV centres in diamond be used as quantum sensors", at first a couple of phosphorus doped samples were measured. The doping concentrations were about 10^16 atoms/cm^3. However, as opposed to the initial measurements, there was no response from any defects/impurities nearby the measured NV centres. There are several potential explanations for this, which are researched currently. The first, a higher phosphorus concentration might be needed to have a fair chance to have a donor close enough to the NV centre. This will be tried by increasing the phosphorus concentration as much as possible. Secondly, the measurement method might be insufficient. To study this, we decided to look at a more "straightforward" (yet new) situation: coupling two NV centres. With the help of QST, we implanted molecules with multiple nitrogen atoms into phosphorus-doped diamond to have a high chance to have NV centres close together. The idea was to first try to use such couples for quantum sensing, as interaction with both NV centres is possible (if their orientation is different), hence it is easier compared to using dark spins. Although we were able to find couples of NV centers with different orientations fairly easily, they were either not stable (probably charge state), or their coherence times were very short (about a microsecond instead of close to a millisecond). Thirdly, we looked at a different measurement method that might be more suitable. The latter we will submit for publication soon.