Department of Physics, University of California, Santa Barbara, California 93106, USA.
Phys Rev Lett. 2019 Oct 4;123(14):146804. doi: 10.1103/PhysRevLett.123.146804.
Surfaces enable useful functionalities for quantum systems, e.g., as interfaces to sensing targets, but often result in surface-induced decoherence where unpaired electron spins are common culprits. Here we show that the coherence time of a near-surface qubit is increased by coherent radio-frequency driving of surface electron spins, where we use a diamond nitrogen-vacancy (NV) center as a model qubit. This technique is complementary to other methods of suppressing decoherence and, importantly, requires no additional materials processing or control of the qubit. Further, by combining driving with the increased magnetic susceptibility of the double-quantum basis, we realize an overall fivefold sensitivity enhancement in NV magnetometry. Informed by our results, we discuss a path toward relaxation-limited coherence times for near-surface NV centers. The surface-spin driving technique presented here is broadly applicable to a wide variety of qubit platforms afflicted by surface-induced decoherence.
表面为量子系统提供了有用的功能，例如作为感应目标的接口，但通常会导致表面诱导退相干，其中不成对电子自旋是常见的罪魁祸首。在这里，我们表明通过对表面电子自旋进行相干射频驱动，可以增加近表面量子位的相干时间，我们使用钻石中的氮空位（NV）中心作为模型量子位。这项技术是对其他抑制退相干方法的补充，重要的是，它不需要额外的材料处理或对量子位的控制。此外，通过将驱动与双量子基的增加的磁灵敏度相结合，我们在 NV 磁强计中实现了整体五倍的灵敏度增强。根据我们的结果，我们讨论了实现近表面 NV 中心弛豫限制相干时间的途径。这里提出的表面自旋驱动技术广泛适用于受到表面诱导退相干影响的各种量子比特平台。
