%0 Journal Article %T Reaching the quantum limit of sensitivity in electron spin resonance %+ Quantronics Group (QUANTRONICS) %+ Bar-Ilan University [Israël] %+ Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 (IEMN) %+ Lawrence Berkeley National Laboratory [Berkeley] (LBNL) %+ Department of Physics and Astronomy [Aarhus] %+ London Centre for Nanotechnology %A Bienfait, A %A Kubo, Y %A Stern, M %A Zhou, Xin %A Schenkel, T %A Vion, D %A Esteve, D %A Julsgaard, B %A Mølmer, K %A Bertet, P. %A Pla, J;j. %A Lo, C.C. %A Morton, J.J.L. %Z Also support by C’Nano IdF through the QUANTROCRYO project. J.J.L.M. is supported by the Royal Society. C.C. Lo is supported by the Royal Commission for the Exhibition of 1851.B. Julsgaard and K. Mølmer acknowledge support from the Villum Foundation. C.D.W.and T.S. acknowledge support from the Office of Science of the US Department of Energyunder contract no. DE-AC02-05CH11231 %< avec comité de lecture %@ 1748-3387 %J Nature Nanotechnology %I Nature Publishing Group %V 11 %P 253-257 %8 2015 %D 2015 %R 10.1038/NNANO.2015.282 %Z Physics [physics]Journal articles %X 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 %G English %2 https://cea.hal.science/cea-01366689/document %2 https://cea.hal.science/cea-01366689/file/nnano.2015.282.pdf %L cea-01366689 %U https://cea.hal.science/cea-01366689 %~ CEA %~ CNRS %~ UNIV-VALENCIENNES %~ IEMN %~ OPENAIRE %~ IRAMIS-SPEC %~ CEA-UPSAY %~ UNIV-PARIS-SACLAY %~ CEA-UPSAY-SACLAY %~ UNIV-LILLE %~ IRAMIS %~ GS-PHYSIQUE %~ INSTITUT-SCIENCES-LUMIERE %~ TEST3-HALCNRS