We demonstrate a nuclear magnetic resonance gyroscope based on the 14N nuclear spins intrinsic to nitrogen-vacancy (NV) centers in diamond. Nuclear spins were polarized and readout optically, without the use of microwave transitions [1]. We used double-quantum nuclear Ramsey technique that increases sensitivity to rotations while suppressing the effect of thermal drifts. The device was mounted on a rotation platform and faithfully reported rotation rates in the range of 5-500 mHz. Significant progress can be expected by switching to bulk 13C nuclear spins in the diamond crystal that will be optically polarized via NV centers.
In this work, we optimize a dynamical decoupling (DD) protocol to improve the spin coherence properties of a dense ensemble of nitrogen-vacancy (NV) centers in diamond. Using liquid nitrogen-based cooling and DD microwave pulses, we increase the transverse coherence time T2 from ∼ 0.7 ms up to ∼ 30 ms. We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. After performing a detailed analysis of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the concatenated XY8 pulse sequences serves as the optimal control scheme for preserving an arbitrary spin state. Finally, we use the concatenated sequences to demonstrate an immediate improvement of the AC magnetic sensitivity up to a factor of two at 250 kHz. For future work, similar protocols may be used to increase coherence times up to NV-NV interaction time scales, a major step toward the creation of quantum collective NV spin states.
KEYWORDS: Diamond, Magnetic sensors, Luminescence, Infrared detectors, Infrared radiation, Fourier transforms, Photonics, Quantum computing, Current controlled current source, Medium wave
We demonstrate magnetometry by detection of the spin state of high-density nitrogen-vacancy (NV) ensembles in diamond using optical absorption at 1042 nm. With this technique, measurement contrast and collection efficiency can approach unity, leading to an increase in magnetic sensitivity compared to the more common method of collecting red fluorescence. Working at 75 K with a sensor with effective volume 50x50x300 μm3, we project photon shot-noise limited sensitivity of 5 pT in one second of acquisition and bandwidth from DC to a few MHz. Operation in a gradiometer configuration yields a noise floor of 7 nTrms at ~110 Hz in one second of acquisition. We also present measurements of the zero-field splitting parameters as a function of temperature, a calibration which is essential for ultra-sensitive magnetometry at low frequencies.
We discuss experimental and theoretical studies of coherent excitation of magnetic sublevels in nD states of cesium that cross in an external electric field. Crossings of mF magnetic sublevels of hyperfine F levels with &Dgr;mF = ±2 lead to resonances in the linearly polarized laser induced fluorescence, while crossings with &Dgr;mF = ±1 lead to resonances in the circularly polarized laser induced fluorescence. These resonances can be exploited to observe alignment to orientation conversion. From the level crossing signals it is possible to measure atomic properties, such as the tensor polarizability &agr;2 and the hyperfine constant A. Alignment to orientation conversion involves the deformation of the spatial distribution of an atom's angular momentum.
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