Robust optical readout and characterization of nuclear spin transitions in nitrogen-vacancy ensembles in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-04-28 |
| Journal | Physical Review Research |
| Authors | A. Jarmola, I. Fescenko, V. M. Acosta, M. W. Doherty, F. K. Fatemi |
| Institutions | DEVCOM Army Research Laboratory, GSI Helmholtz Centre for Heavy Ion Research |
| Citations | 21 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Robust Nuclear Spin Readout in NV Diamond
Section titled âTechnical Documentation & Analysis: Robust Nuclear Spin Readout in NV DiamondâThis document analyzes the research paper âRobust optical readout and characterization of nuclear spin transitions in nitrogen-vacancy ensembles in diamondâ and outlines how 6CCVDâs advanced MPCVD diamond materials and fabrication services can accelerate and enhance similar quantum sensing and information processing projects.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a robust, direct optical readout mechanism for the 14N nuclear spin ensemble within diamond Nitrogen-Vacancy (NV) centers, achieving performance metrics critical for next-generation quantum sensors.
- High Readout Contrast: Achieved nuclear Rabi oscillation contrast up to 3.8%, comparable to the contrast typically realized with NV electron spins, enabling highly efficient optical detection.
- Enhanced Robustness: Characterization of the nuclear quadrupole coupling constant (Q) revealed a temperature dependence (d|Q|/dT = -35.0(2) Hz/K at 297 K) that is approximately 2000 times smaller than the corresponding electron spin parameter (D).
- Quantum Sensing Advantage: This extreme robustness against temperature and magnetic field fluctuations makes the 14N nuclear spin an ideal candidate for precision quantum sensing applications, such as gyroscopes and clocks.
- Material Requirements: The experiment relied on high-quality, low-nitrogen diamond (HPHT, ~50 ppm N) subsequently processed via high-energy electron irradiation (10 MeV, 1018 cm-2 dose) and high-temperature annealing (800 °C).
- 6CCVD Value Proposition: 6CCVD provides superior MPCVD Single Crystal Diamond (SCD) substrates with ultra-low, controlled nitrogen purity, optimized for precise NV creation and integration into complex quantum devices.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper, highlighting the key performance metrics and experimental conditions.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Rabi Contrast (C) | 3.8 | % | Observed for 14N nuclear spin transitions |
| Coherence Time (T2*) Range | 0.5 - 0.8 | ms | Measured via Ramsey interferometry |
| Quadrupole Coupling Constant (Q) | -4.9457(3) | MHz | Determined via fit at 300 K |
| Q Temperature Slope (d | Q | /dT) | -35.0(2) |
| Robustness Factor (Q vs D) | ~2000 | Times | Q is less temperature-dependent than D |
| Magnetic Field Range (Rabi) | 450 - 550 | G | Range where contrast C > 2% |
| Temperature Range Studied | 77.5 - 420 | K | Range of characterization |
| Initial Nitrogen Concentration | ~50 | ppm | HPHT substrate specification |
| Electron Irradiation Dose | ~1018 | cm-2 | Used for NV creation |
| Annealing Temperature | 800 | °C | Vacuum annealing post-irradiation |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success hinges on precise material preparation and advanced spectroscopic techniques.
- Substrate Selection: A [100]-cut High-Pressure High-Temperature (HPHT) diamond with an initial nitrogen concentration of approximately 50 ppm was used.
- NV Center Generation: NV ensembles were created by irradiating the diamond with 10 MeV electrons at a dose of ~1018 cm-2, followed by vacuum annealing at 800 °C for three hours.
- Optical Excitation: A custom confocal microscopy setup was used, employing a 532 nm laser (20 mW power, 20 ”s pulse duration) for optical pumping and readout.
- Fluorescence Collection: Fluorescence was collected through the objective and filtered using a 650-800 nm bandpass filter, detected by a Si avalanche photodiode.
- Field Delivery: Static magnetic field (B) was applied along the NV axis using a neodymium permanent magnet. Radio-frequency (RF) and microwave (MW) magnetic fields were delivered via a 100 ”m diameter copper wire placed directly on the diamond surface.
- Measurement Techniques: Optically Detected Nuclear Magnetic Resonance (ODNMR) spectroscopy and Ramsey interferometry were utilized to measure transition frequencies, Rabi oscillations, and spin-coherence times (T2*).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVDâs expertise in MPCVD diamond growth and advanced fabrication services directly addresses the material and integration challenges inherent in replicating and scaling this high-performance quantum sensing research.
Applicable Materials
Section titled âApplicable MaterialsâThe research utilized HPHT diamond with 50 ppm nitrogen. For next-generation quantum sensors requiring tighter control over NV density and improved coherence times, 6CCVD recommends MPCVD SCD materials:
- Electronic Grade SCD (Ultra-High Purity): Recommended for projects requiring the lowest possible native nitrogen concentration (< 1 ppb). This allows for precise, controlled NV creation via post-growth irradiation, leading to lower NV density and potentially maximizing the nuclear spin coherence time (T2*).
- Optical Grade SCD: Ideal for applications where high optical transmission and low scattering are critical across the 532 nm to 800 nm range used in the experiment.
- Custom Doped SCD: 6CCVD can grow SCD with controlled, low-level nitrogen doping (e.g., 1 ppm to 50 ppm) during the CVD process, eliminating the need for high-dose irradiation and ensuring uniform NV concentration throughout the substrate.
Customization Potential
Section titled âCustomization PotentialâThe use of external 100 ”m copper wires for RF/MW delivery introduces alignment challenges and field inhomogeneity. 6CCVD offers integrated solutions to enhance device performance and scalability:
| Requirement from Paper | 6CCVD Custom Solution | Technical Advantage |
|---|---|---|
| Substrate Material | Single Crystal Diamond (SCD) | Superior purity and lattice quality compared to HPHT. |
| Substrate Orientation | Custom [100] Orientation | Guaranteed crystal orientation for alignment with the NV axis. |
| Dimensions & Thickness | Custom Plates/Wafers | SCD thickness control from 0.1 ”m up to 500 ”m. |
| RF/MW Delivery | Integrated Metalization | Internal capability for depositing Ti/Pt/Au, Cu, or W structures (e.g., coplanar waveguides) directly onto the diamond surface. |
| Surface Quality | Ultra-Low Roughness Polishing | SCD polishing to Ra < 1 nm for minimized surface noise and enhanced optical coupling efficiency (η). |
Engineering Support
Section titled âEngineering Supportâ6CCVD operates as a technical partner, not just a supplier. Our in-house PhD team specializes in optimizing diamond substrates for quantum applications.
- NV Optimization: We provide substrates specifically optimized for post-growth processing (irradiation and annealing at temperatures up to 800 °C, as used in this study).
- Material Selection for Rotation Sensing: Our experts assist researchers in selecting the optimal material purity and crystal orientation to maximize the minimum detectable change in rotation rate (ÎŽÏ), balancing high contrast (C) and long coherence time (T2*).
- Integration Support: Consultation on integrating on-chip RF/MW structures to improve the homogeneity and efficiency of the Rabi driving fields.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Nuclear spin ensembles in diamond are promising candidates for quantum sensing applications, including rotation sensing. Here we characterize the optically detected nuclear spin transitions associated with the N-14 nuclear spin within diamond nitrogen-vacancy (NV) centers. We observe that the contrast of the nuclearspin-dependent fluorescence is comparable to the contrast of the NV electron-spin-dependent fluorescence. Using Ramsey spectroscopy, we investigate the temperature and magnetic field dependence of the nuclear spin transitions in the 77.5-420 K and 350-675 G range, respectively. The nuclear quadrupole coupling constant Q was found to vary with temperature T, yielding d vertical bar Q vertical bar/dT =-35.0(2) Hz/K at T = 297 K. The temperature and magnetic field dependencies reported here are important for quantum sensing applications such as rotation sensing and potentially for applications in quantum information processing.