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Reaching the quantum limit of sensitivity in electron spin resonance

Abstract : The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science 1 , from in vivo imaging 2 to distance measurements in spin-labelled proteins 3. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here, using a Josephson parametric microwave amplifier combined with high-quality-factor super-conducting microresonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude 4,5. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn 6 echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr–Purcell– Meiboom–Gill sequence 7. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. The detection volume of our resonator is ∼0.02 nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale
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Submitted on : Thursday, September 15, 2016 - 10:57:41 AM
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A Bienfait, Y Kubo, M Stern, Xin Zhou, T Schenkel, et al.. Reaching the quantum limit of sensitivity in electron spin resonance. Nature Nanotechnology, Nature Publishing Group, 2015, 11, pp.253-257. ⟨10.1038/NNANO.2015.282⟩. ⟨cea-01366689⟩



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