Cavity-enhanced microwave readout of a solid-state spin sensor

Erik R Eisenach,Michael F O’Keeffe,Dirk R Englund,Matthew H Steinecker,Danielle A Braje,Jennifer M Schloss,John F Barry

doi:10.1038/s41467-021-21256-7

Erik R Eisenach, Michael F O’Keeffe + Show 5 more

Open Access

https://doi.org/10.1038/s41467-021-21256-7

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Abstract

Overcoming poor readout is an increasingly urgent challenge for devices based on solid-state spin defects, particularly given their rapid adoption in quantum sensing, quantum information, and tests of fundamental physics. However, in spite of experimental progress in specific systems, solid-state spin sensors still lack a universal, high-fidelity readout technique. Here we demonstrate high-fidelity, room-temperature readout of an ensemble of nitrogen-vacancy centers via strong coupling to a dielectric microwave cavity, building on similar techniques commonly applied in cryogenic circuit cavity quantum electrodynamics. This strong collective interaction allows the spin ensemble’s microwave transition to be probed directly, thereby overcoming the optical photon shot noise limitations of conventional fluorescence readout. Applying this technique to magnetometry, we show magnetic sensitivity approaching the Johnson–Nyquist noise limit of the system. Our results pave a clear path to achieve unity readout fidelity of solid-state spin sensors through increased ensemble size, reduced spin-resonance linewidth, or improved cavity quality factor.

Highlights

Overcoming poor readout is an increasingly urgent challenge for devices based on solid-state spin defects, given their rapid adoption in quantum sensing, quantum information, and tests of fundamental physics
Alternative readout techniques have been developed to increase measurement fidelity, but most have focused on single spins and small ensembles[7,8,9,10,11,12,13,14,15,16], which limits their utility for high-sensitivity measurements[6]
Related cavity quantum electrodynamics (CQED) effects have been employed for quantum information applications in cryogenic solid-state[21,22,23,24,25,26,27,28] and superconducting qubit[29,30,31] systems

Summary

Introduction

Overcoming poor readout is an increasingly urgent challenge for devices based on solid-state spin defects, given their rapid adoption in quantum sensing, quantum information, and tests of fundamental physics. We demonstrate high-fidelity, room-temperature readout of an ensemble of nitrogen-vacancy centers via strong coupling to a dielectric microwave cavity, building on similar techniques commonly applied in cryogenic circuit cavity quantum electrodynamics This strong collective interaction allows the spin ensemble’s microwave transition to be probed directly, thereby overcoming the optical photon shot noise limitations of conventional fluorescence readout. In addition to providing unity measurement contrast and circumventing the shot-noise limitation inherent to conventional optical spin readout, the readout method introduces no substantial overhead time to measurements and results in an advantageous cavity-mediated narrowing of the magnetic resonance features This advance promises what has long been elusive for quantum sensors based on solid-state spin ensembles: a clear avenue to readout at the spin-projection limit. Detection of the transmission through or reflection from the composite cavity provides readout of the spin resonance[34]

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