Bryan Myers

Engineering shallow spins in diamond with nitrogen delta-doping

We demonstrate nanometer-precision depth control of nitrogen-vacancy (NV) center creation near the surface of synthetic diamond using an in situ nitrogen delta-doping technique during plasma-enhanced chemical vapor deposition. Despite their proximity to the surface, doped NV centers with depths (d) ranging from 5 to 100 nm display long spin coherence times, T2 > 100 μs at d = 5 nm and T2 > 600 μs at d ≥ 50 nm. The consistently long spin coherence observed in such shallow NV centers enables applications such as atomic-scale external spin sensing and hybrid quantum architectures.

Dynamic strain-mediated coupling of a single diamond spin to a mechanical resonator

The development of hybrid quantum systems is central to the advancement of emerging quantum technologies, including quantum information science and quantum-assisted sensing. The recent demonstration of high-quality single-crystal diamond resonators has led to significant interest in a hybrid system consisting of nitrogen–vacancy centre spins that interact with the resonant phonon modes of a macroscopic mechanical resonator through crystal strain. However, the nitrogen–vacancy spin–strain interaction has not been well characterized. Here, we demonstrate dynamic, strain-mediated coupling of the mechanical motion of a diamond cantilever to the spin of an embedded nitrogen–vacancy centre. Via quantum control of the spin, we quantitatively characterize the axial and transverse strain sensitivities of the nitrogen–vacancy ground-state spin. The nitrogen–vacancy centre is an atomic scale sensor and we demonstrate spin-based strain imaging with a strain sensitivity of 3 × 10−6 strain Hz−1/2. Finally, we show how this spin-resonator system could enable coherent spin–phonon interactions in the quantum regime.

High quality factor single-crystal diamond mechanical resonators

Single-crystal diamond is a promising material for microelectromechanical systems (MEMs) because of its low mechanical loss, compatibility with extreme environments, and built-in interface to high-quality spin centers. But its use has been limited by challenges in processing and growth. We demonstrate a wafer bonding-based technique to form diamond on insulator, from which we make single-crystal diamond micromechanical resonators with mechanical quality factors as high as 338 000 at room temperature. Variable temperature measurements down to 10 K reveal a nonmonotonic dependence of quality factor on temperature. These resonators enable integration of single-crystal diamond into MEMs technology for classical and quantum applications.

Two-Dimensional Nanoscale Imaging of Gadolinium Spins via Scanning Probe Relaxometry with a Single Spin in Diamond

Spin-labeling of molecules with paramagnetic ions is an important approach for determining molecular structure, however current ensemble techniques lack the sensitivity to detect few isolated spins. In this Letter, we demonstrate two-dimensional nanoscale imaging of paramagnetic gadolinium compounds using scanning relaxometry of a single nitrogen vacancy (NV) center in diamond. Gadopentetate dimeglumine attached to an atomic force microscope tip is controllably interacted with and detected by the NV center, by virtue of the fact that the NV exhibits fast relaxation in the fluctuating magnetic field generated by electron spin flips in the gadolinium. Using this technique, we demonstrate a reduction in the

Three-dimensional localization of spins in diamond using 12C implantation

T_1

Patterned Formation of Highly Coherent Nitrogen-Vacancy Centers Using a Focused Electron Irradiation Technique

relaxation time of the NV center by over two orders of magnitude, probed with a spatial resolution of 20 nm. Our result exhibits the viability of the technique for imaging individual spins attached to complex nanostructures or biomolecules, along with studying the magnetic dynamics of isolated spins.

Reduced Plasma-Induced Damage to Near-Surface Nitrogen-Vacancy Centers in Diamond

We demonstrate three-dimensional localization of a single nitrogen-vacancy (NV) center in diamond by combining nitrogen doping during growth with a post-growth 12C implantation technique that facilitates vacancy formation in the crystal. We show that the NV density can be controlled by the implantation dose without necessitating increase of the nitrogen incorporation. By implanting a large 12C dose through nanoscale apertures, we can localize an individual NV center within a volume of (∼180 nm)3 at a deterministic position while repeatedly preserving a coherence time (T2) > 300 μs. This deterministic position control of coherent NV centers enables integration into NV-based nanostructures to realize scalable spin-sensing devices as well as coherent spin coupling mediated by photons and phonons.

Double-Quantum Spin-Relaxation Limits to Coherence of Near-Surface Nitrogen-Vacancy Centers

We demonstrate fully three-dimensional and patterned localization of nitrogen-vacancy (NV) centers in diamond with coherence times in excess of 1 ms. Nitrogen δ-doping during chemical vapor deposition diamond growth vertically confines nitrogen to 4 nm while electron irradiation with a transmission electron microscope laterally confines vacancies to less than 450 nm. We characterize the effects of electron energy and dose on NV formation. Importantly, our technique enables the formation of reliably high-quality NV centers inside diamond nanostructures with applications in quantum information and sensing.

Hyperfine-enhanced gyromagnetic ratio of a nuclear spin in diamond

Understanding plasma etch damage on near-surface nitrogen vacancy (NV) centers in diamond is essential for preserving NV emission in photonic structures and magnetometry systems. We have developed a methodology to compare the optical properties of ensemble NV centers initially 70 nm from the surface brought closer to the surface through etching with O2 plasmas in three different reactors. We employ a conventional reactive ion etcher, a barrel etcher, and a downstream etcher. We find that, irrespective of the etcher used, NV luminescence dims steadily as NVs are brought closer to the surface due to optical and surface effects. When NVs are less than 40 nm from the surface, differences in damage from the three different plasma processes affect the NV emission intensity in different ways. Diamond that is etched using the conventional etching method shows a greatly reduced NV luminescence, whereas NVs 15 nm from the surface still survive when the diamond is etched in the downstream reactor. As a result, downstream etching provides a possible alternative method for low damage etching of diamond for preservation of near surface NV properties.

Probing surface noise with depth-calibrated spins in diamond.

We probe the relaxation dynamics of the full three-level spin system of near-surface nitrogen-vacancy (NV) centers in diamond to define a T_{1} relaxation time that sets the T_{2}≤2T_{1} coherence limit of the NVs subset qubit superpositions. We find that double-quantum spin relaxation via electric field noise dominates T_{1} of near-surface NVs at low applied magnetic fields. Furthermore, we differentiate 1/f^{α} spectra of electric and magnetic field noise using a novel noise-spectroscopy technique, with broad applications in probing surface-induced decoherence at material interfaces.