Reaching the quantum limit of sensitivity in electron spin resonance

A Bienfait (1) , Y Kubo (1) , M Stern (2, 1) , Xin Zhou (1, 3) , T Schenkel (4) , D Vion (1) , D Esteve (1) , B Julsgaard (5) , K Mølmer (5) , P. Bertet (1) , J;j. Pla (6) , C.C. Lo (6) , J.J.L. Morton (6)

1 QUANTRONICS - Quantronics Group
2 Bar-Ilan University [Israël]
3 IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520
4 LBNL - Lawrence Berkeley National Laboratory [Berkeley]
5 Department of Physics and Astronomy [Aarhus]
6 London Centre for Nanotechnology

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

Domains: Physics [physics]

A Bienfait, Y Kubo, M Stern, Xin Zhou, T Schenkel, et al.. Reaching the quantum limit of sensitivity in electron spin resonance. Nature Nanotechnology, 2015, 11, pp.253-257. ⟨10.1038/NNANO.2015.282⟩. ⟨cea-01366689⟩