Abstract
The nitrogen-vacancy (NV) center in diamond exhibits spin-dependent fluorescence and long spin coherence times under ambient conditions, enabling applications in quantum information processing and sensing. NV centers near the surface can have strong interactions with external materials and spins, enabling new forms of nanoscale spectroscopy. However, NV spin coherence degrades within 100 nm of the surface, suggesting that diamond surfaces are plagued with ubiquitous defects. Prior work on characterizing near-surface noise has primarily relied on using NV centers themselves as probes; while this has the advantage of exquisite sensitivity, it provides only indirect information about the origin of the noise. Here we demonstrate that surface spectroscopy methods and single-spin measurements can be used as complementary diagnostics to understand sources of noise. We find that surface morphology is crucial for realizing reproducible chemical termination, and use this insight to achieve a highly ordered, oxygen-terminated surface with suppressed noise. We observe NV centers within 10 nm of the surface with coherence times extended by an order of magnitude.
- Received 19 March 2019
- Revised 27 May 2019
DOI:https://doi.org/10.1103/PhysRevX.9.031052
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
In diamond, atomic defects known as color centers are promising tools for many quantum technologies, including quantum information processing and quantum sensing. For the latter application, a particularly exciting direction is to leverage the nearly atomic-scale spatial resolution of these sensors to probe the magnetic fields emanating from molecules and materials, giving information about their structure and dynamics. Bringing nitrogen-vacancy (NV) centers close to sensing targets also requires that they are close to the diamond surface; however, noise from the surface itself significantly reduces the sensitivity. By studying the diamond surface using several spectroscopy techniques, we have developed a way to reduce this noise tenfold, paving the way for significantly improved sensors.
Gaining precise control over the diamond surface is challenging because of its hardness and chemical inertness. We combine laboratory and synchrotron-based surface spectroscopy and single-spin measurements to understand the sources of noise at the diamond surface, and we use these insights to create a highly ordered, oxygen-terminated surface. We observe NV centers within 10 nm of the surface with coherence times extended by an order of magnitude.
These improved NV substrates can immediately be deployed in sensing applications, including magnetic resonance imaging of single molecules and nanoscale imaging of currents and spin textures in condensed-matter systems. Our approach of combining surface spectroscopy with single-spin measurements can also be applied for the development of novel surface terminations in diamond and, more generally, to study other quantum information platforms such as superconducting qubits, trapped ions, and shallow donors.
