title: 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, from in vivo imaging to distance measurements in spin-labelled proteins. 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 superconducting microresonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. 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.
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: A
authors.initials: A
authors.lastname: Bienfait
authors.affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK.
authors.forename: J J
authors.initials: JJ
authors.lastname: Pla
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0001-5803-4287
authors.initials: Y
authors.lastname: Kubo
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.|Quantum Nanoelectronics Laboratory, BINA, Bar Ilan University, Ramat Gan, Israel.
authors.forename: M
authors.initials: M
authors.lastname: Stern
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.|ISEN Department, Institute of Electronics Microelectronics and Nanotechnology, CNRS UMR 8520, Avenue Poincaré, CS 60069, Villeneuve d'Ascq Cedex 59652, France.
authors.forename: X
authors.initials: X
authors.lastname: Zhou
authors.affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK.
authors.forename: C C
authors.initials: CC
authors.lastname: Lo
authors.affiliation: Accelerator Technology and Applied Physics Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Weis
authors.affiliation: Accelerator Technology and Applied Physics Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: T
authors.initials: T
authors.lastname: Schenkel
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
authors.forename: M L W
authors.initials: ML
authors.lastname: Thewalt
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Vion
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Esteve
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, Aarhus C DK-8000, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Julsgaard
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, Aarhus C DK-8000, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Mølmer
authors.affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK.
authors.forename: J J L
authors.initials: JJ
authors.lastname: Morton
authors.affiliation: Quantronics Group, SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: Bertet
mesh_terms: D000389:Air Conditioning / Q000295:instrumentation; D000669:Amplifiers, Electronic; D007562:Creutzfeldt-Jakob Syndrome; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008832:Microchemistry / Q000295:instrumentation*; D008872:Microwaves; D008904:Miniaturization; D053758:Nanoparticles / Q000032:analysis* / Q000737:chemistry*; D011789:Quantum Theory; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio