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

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.

Cavity Quantum Electrodynamics Effects with Nitrogen Vacancy Center Spins in Diamond and Microwave Resonators at Room Temperature

“…( In the simulations, we assume parameters compatible with the stimulated superradiance pulse experiment at cryogenic temperature [8], see Appendix C. Here, we consider a dielectric resonator of same Q-factor at room-temperature (see Ref. [9][10][11][12]).…”

“…1(b). Note that the strong collective coupling may have been present in the recent room-temperature experiments on continuous wave maser [9] and dispersive readout of NV − spins [10,11] and C-QED effects with the spins in pentacene's lowest triplet states [12]. Panel (a) shows a 3D lumped element resonator operating in a cryogenic environment at 25 mK (left), as used in [8], where the spin-ensemble is in equilibrium with the cooled environment (right).…”

“…The inset panels show the Dicke states of the spin-ensemble with increasing J for increasing ηs. The simulations were done with parameters compatible with the Rabi oscillation experiment at cryogenic temperature[7], see Appendix C. Here, we consider a dielectric resonator of same Q-factor at room-temperature (see Ref [9][10][11][12]…”

Enhanced quantum sensing with room-temperature solid-state masers

“…The masing-enhanced readout is advantageous over conventional optical readout in terms of the single-shot SNR and overhead time. We note that our readout protocol would seem to enrich the rising field of microwave readout [35,36] for quantum sensing and enables microwave readout with (i) a higher SNR; (ii) an appealing threshold-like (non-linear) enhancement of the sensitivity η with increasing number of spins N , whereas the dependence of η on N is linear and square root for alternative microwave readout [35,36] and conventional optical readout protocols, respectively. Furthermore, this technique is fully compatible with the extensively studied solid-state spin sensors based on NV diamond and V Si in SiC, which are both candidates for room-temperature solid-state masers [18,19,31], and it can also be used to explore exotic quantum sensors (e.g.…”

Electron-to-nuclear spectral mapping via "Galton board" dynamic nuclear polarization

“…From a technological perspective, we envision applications in RF ( 13 C) interrogated NV-center magnetometry, without the use of a MW cavity [45]. As opposed to optical NV sensors, this can permit DC magnetometers that function in turbid or scattering media and with arbitrarily oriented crystals.…”