Zvi Uri, Candido Denis R, Weiss Adam M, Jones Aidan R, Chen Lingjie, Golovina Iryna, Yu Xiaofei, Wang Stella, Talapin Dmitri V, Flatté Michael E, Esser-Kahn Aaron P, Maurer Peter C
Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637.
Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242.
Proc Natl Acad Sci U S A. 2025 May 27;122(21):e2422542122. doi: 10.1073/pnas.2422542122. Epub 2025 May 21.
Fluorescent diamond nanocrystals can host spin qubit sensors capable of probing the physical properties of biological systems with nanoscale spatial resolution. Sub-100 nm diamond nanosensors can readily be delivered into intact cells and even living organisms. However, applications beyond current proof-of-principle experiments require a substantial increase in sensitivity, which is limited by surface induced charge instability and electron-spin dephasing. In this work, we utilize engineered core-shell structures to achieve a drastic increase in qubit coherence times () from 1.1 to 35 μs in bare nanodiamonds to upward of 52 to 87 μs. We use electron-paramagnetic-resonance results to present a band bending model and connect silica encapsulation to the removal of deleterious mid-gap surface states that are negatively affecting the qubit's spin properties. Combined with a 1.9-fold increase in particle luminescence these advances correspond to up to two-order-of-magnitude reduction in integration time. Probing qubit dynamics at a single particle level further reveals that the noise characteristics fundamentally change from a bath with spins that rearrange their spatial configuration during the course of an experiment to a more dilute static bath. The observed results shed light on the underlying mechanisms governing fluorescence and spin properties in diamond nanocrystals and offer an effective noise mitigation strategy based on engineered core-shell structures.
荧光金刚石纳米晶体可承载自旋量子比特传感器，能够以纳米级空间分辨率探测生物系统的物理特性。尺寸小于100 nm的金刚石纳米传感器可以很容易地被递送至完整细胞甚至活生物体中。然而，要超越当前的原理验证实验进行应用，需要大幅提高灵敏度，而灵敏度受到表面诱导电荷不稳定性和电子自旋退相的限制。在这项工作中，我们利用工程化的核壳结构，将裸纳米金刚石中的量子比特相干时间（）从1.1 μs大幅提高到35 μs，再到52至87 μs以上。我们利用电子顺磁共振结果提出了一个能带弯曲模型，并将二氧化硅封装与去除有害的带隙中间表面态联系起来，这些表面态对量子比特的自旋特性产生负面影响。结合粒子发光提高1.9倍，这些进展相应地使积分时间减少了高达两个数量级。在单粒子水平上探测量子比特动力学进一步揭示，噪声特性从在实验过程中自旋重新排列其空间构型的热库，从根本上转变为更稀薄的静态热库。观察到的结果揭示了金刚石纳米晶体中荧光和自旋特性的潜在机制，并提供了一种基于工程化核壳结构的有效噪声缓解策略。
