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High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature



Magnetic resonance techniques not only provide powerful imaging tools that have revolutionized medicine, but they have a wide spectrum of applications in other fields of science such as biology, chemistry, neuroscience and physics. However, current state-of-the-art magnetometers are unable to detect a single nuclear spin unless the tip-to-sample separation is made sufficiently small. Here, we demonstrate theoretically that by placing a ferromagnetic particle between a nitrogen–vacancy magnetometer and a target spin, the magnetometer sensitivity is improved dramatically. Using materials and techniques that are already experimentally available, our proposed set-up is sensitive enough to detect a single nuclear spin within ten milliseconds of data acquisition at room temperature. The sensitivity is practically unchanged when the ferromagnet surface to the target spin separation is smaller than the ferromagnet lateral dimensions; typically about a tenth of a micrometre. This scheme further benefits when used for nitrogen–vacancy ensemble measurements, enhancing sensitivity by an additional three orders of magnitude.

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Figure 1: Set-up.
Figure 2: The pulse sequence applied to the qubit (black) and to the NV-centre spin (red).
Figure 3: Contour plot of the quantity |B+ · ns|/|B+| in the x–y plane 2 nm above the upper face of the cube.
Figure 4: The FM energy when an external field b/ba = 0.2 is applied.


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The authors thank H. Fanghor for sharing his expertise about micromagnetic simulations. This work was supported by the Swiss National Science Foundation, the National Centre of Competence in Research, Quantum Science and Technology, Diamond Devices Enabled Metrology and Sensing, Intelligence Advanced Research Projects Activity, the Defense Advanced Research Projects Agency, Quantum-Assisted Sensing and Readout programmes and the Multidisciplinary University Research Initiative, Qubit Enabled Imaging, Sensing, and Metrology. F.L.P. acknowledges support from the Alexander von Humboldt Foundation.

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L.T. and F.P. performed the calculations and numerical simulations. L.T. and D.L. were responsible for the project planning. All the authors contributed to the discussions and writing. D.L. initiated and supervised the work.

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Correspondence to Daniel Loss.

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Trifunovic, L., Pedrocchi, F., Hoffman, S. et al. High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature. Nature Nanotech 10, 541–546 (2015).

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