Abstract
Quantum spin dephasing is caused by inhomogeneous coupling to the environment, with resulting limits to the measurement time and precision of spin-based sensors. The effects of spin dephasing can be especially pernicious for dense ensembles of electronic spins in the solid-state, such as for nitrogen-vacancy (NV) color centers in diamond. We report the use of two complementary techniques, spin bath control and double quantum coherence, to enhance the inhomogeneous spin dephasing time ($T_2^*$) for NV ensembles by more than an order of magnitude. In combination, these quantum control techniques (i) eliminate the effects of the dominant NV spin ensemble dephasing mechanisms, including crystal strain gradients and dipolar interactions with paramagnetic bath spins, and (ii) increase the effective NV gyromagnetic ratio by a factor of two. Applied independently, spin bath control and double quantum coherence elucidate the sources of spin dephasing over a wide range of NV and spin bath concentrations. These results demonstrate the longest reported $T_2^*$ in a solid-state electronic spin ensemble at room temperature, and outline a path towards NV-diamond magnetometers with broadband femtotesla sensitivity.
Highlights
Solid-state electronic spins, including defects in silicon carbide [1,2,3,4,5], phosphorus spins in silicon [6,7], and silicon-vacancy [3,8,9] and nitrogen-vacancy (NV) centers [10] in diamond, have garnered increasing relevance for quantum science and sensing experiments
We report the use of two complementary techniques, spin-bath driving, and double quantum coherence magnetometry, to enhance the inhomogeneous spin dephasing time (TÃ2) for NV ensembles by more than an order of magnitude
We show that these quantum control techniques can extend the NV spin ensemble TÃ2 by more than an order of magnitude
Summary
Solid-state electronic spins, including defects in silicon carbide [1,2,3,4,5], phosphorus spins in silicon [6,7], and silicon-vacancy [3,8,9] and nitrogen-vacancy (NV) centers [10] in diamond, have garnered increasing relevance for quantum science and sensing experiments. For NV ensembles, the dc magnetic-field sensitivity is typically limited by dephasing of the NV sensor spins. In such instances, spin interactions with an inhomogeneous environment [see Fig. 1(a)] limit the experimental sensing time to the spin dephasing time
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