title: Optimized quantum sensing with a single electron spin using real-time adaptive measurements.
abstract: Quantum sensors based on single solid-state spins promise a unique combination of sensitivity and spatial resolution. The key challenge in sensing is to achieve minimum estimation uncertainty within a given time and with high dynamic range. Adaptive strategies have been proposed to achieve optimal performance, but their implementation in solid-state systems has been hindered by the demanding experimental requirements. Here, we realize adaptive d.c. sensing by combining single-shot readout of an electron spin in diamond with fast feedback. By adapting the spin readout basis in real time based on previous outcomes, we demonstrate a sensitivity in Ramsey interferometry surpassing the standard measurement limit. Furthermore, we find by simulations and experiments that adaptive protocols offer a distinctive advantage over the best known non-adaptive protocols when overhead and limited estimation time are taken into account. Using an optimized adaptive protocol we achieve a magnetic field sensitivity of 6.1 ± 1.7 nT Hz(-1/2) over a wide range of 1.78 mT. These results open up a new class of experiments for solid-state sensors in which real-time knowledge of the measurement history is exploited to obtain optimal performance.
authors.affiliation: QuTech and Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, GA Delft 2600, The Netherlands.
authors.forename: C
authors.initials: C
authors.lastname: Bonato
authors.affiliation: QuTech and Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, GA Delft 2600, The Netherlands.
authors.forename: M S
authors.initials: MS
authors.lastname: Blok
authors.affiliation: Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109, Australia.|Center for Engineered Quantum Systems, Macquarie University, Sydney, New South Wales 2109, Australia.
authors.forename: H T
authors.initials: HT
authors.lastname: Dinani
authors.affiliation: Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109, Australia.
authors.forename: D W
authors.initials: DW
authors.lastname: Berry
authors.affiliation: Element Six Ltd, Kings Ride Park, Ascot, Berkshire SL5 8BP, UK.
authors.forename: M L
authors.initials: ML
authors.lastname: Markham
authors.affiliation: Element Six Ltd, Kings Ride Park, Ascot, Berkshire SL5 8BP, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Twitchen
authors.affiliation: QuTech and Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, GA Delft 2600, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Hanson