Determination of the position of a single nuclear spin from free nuclear precessions detected by a solid-state quantum sensor
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-09-13 |
| Journal | Physical review. B./Physical review. B |
| Authors | Kento Sasaki, Kohei M. Itoh, Eisuke Abe |
| Institutions | Keio University |
| Citations | 24 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Nanoscale Quantum Sensing for Single-Spin MRI
Section titled âTechnical Documentation and Analysis: Nanoscale Quantum Sensing for Single-Spin MRIâSource Paper: Determination of the Position of a Single Nuclear Spin from Free Nuclear Precessions Detected by a Solid-State Quantum Sensor
Executive Summary
Section titled âExecutive SummaryâThis research pioneers a critical advance in solid-state Nuclear Magnetic Resonance (NMR) by uniquely determining the complete 3D spatial coordinates (distance $r$, polar angle $\theta$, and azimuthal angle $\phi$) of a single ${}^{13}\text{C}$ nuclear spin within a diamond lattice. This achievement leverages the exceptional sensitivity of the Nitrogen-Vacancy (NV) center in diamond, marking a major step toward single-molecular magnetic resonance imaging (MRI).
- Core Breakthrough: Unique determination of the azimuthal angle ($\phi$) of a single ${}^{13}\text{C}$ spin, a parameter previously inaccessible via standard multi-pulse quantum sensing protocols.
- Methodology: Integration of pulsed Dynamic Nuclear Polarization (PulsePol) for spin preparation, a phase-controlled Radiofrequency (RF) tipping pulse, and a multi-pulse AC sensing sequence (Carr-Purcell, CP) combined with a novel $(\pi/2)_{y}$ readout pulse.
- Material Necessity: The protocol relies critically on the coherence and isolation provided by an atomic-scale quantum sensor (NV center) embedded in highly pure, high-quality Type-IIa Single Crystal Diamond (SCD).
- Precision Engineering: Requires precise calibration of microwave and RF delivery systems integrated directly onto or adjacent to the diamond substrate (copper wire stripline, hand-wound coil).
- Application Potential: This technique facilitates nanoscale NMR spectroscopy and offers a roadmap for high-resolution chemical structure analysis and 3D mapping at the single-molecule level.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters and outcomes define the experimental performance and physical characteristics required for this quantum sensing protocol:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | Type-IIa (001) Substrate | N/A | Essential for low nitrogen concentration and high-coherence NV centers. |
| Sensor Type | Single Isolated NV Center | N/A | Located approximately ~50 ”m in bulk diamond. |
| Target Spin | Single ${}^{13}\text{C}$ Nuclear Spin | N/A | Used as the test nucleus. Natural abundance (1.1%). |
| Static Magnetic Field ($B_{0}$) | 36.2 | mT | Applied along the [111] crystallographic direction. |
| NV Zero-Field Splitting ($D$) | 2870.4 | MHz | Determined through vector DC magnetometry. |
| Target Spin Coordinates ($r$) | 6.84 | Ă | Distance from the NV sensor. |
| Target Spin Polar Angle ($\theta$) | $94.8^{\circ}$ | Degrees | Tilt from the applied $B_{0}$ direction. |
| Target Spin Azimuthal Angle ($\phi$) | $250.9^{\circ}$ | Degrees | Uniquely determined lattice site position. |
| **Parallel Hyperfine Coupling ($A_{ | }$)** | -173.1 | |
| Perpendicular Hyperfine Coupling ($A_{\perp}$) | 22.3 | kHz | Derived from correlation spectroscopy. Accuracy ± 0.1 kHz. |
| RF $\pi$ Pulse Length | 199.443 | ”s | Matched to 43 oscillation periods of $f_{1}$. |
| RF $\pi/2$ Pulse Length | 102.041 | ”s | Matched to 22 oscillation periods of $f_{1}$. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relies on precise control over the electronic and nuclear spins using a sequence of calibrated pulses and specific material configurations:
- Material Preparation and NV Selection: Use of a high-purity Type-IIa (001) SCD substrate. A single NV center, with its symmetry axis aligned along the [111] direction, is optically resolved using a 515-nm confocal microscope.
- Magnetic Field Calibration: A static field $B_{0}$ (36.2 mT) is aligned to the NV symmetry axis. Microwave (MW) and Radiofrequency (RF) delivery components (copper wire stripline for MW, hand-wound coil for RF) are calibrated for optimal field direction and homogeneity.
- Initial Characterization (CP/Correlation Spectroscopy): Carr-Purcell (CP) sequences and correlation spectroscopy are used to identify the target ${}^{13}\text{C}$ nuclear spin and precisely determine the hyperfine parameters ($A_{||}$, $A_{\perp}$) and associated Larmor frequencies ($f_{0}$, $f_{1}$).
- Nuclear Spin Polarization (PulsePol): The PulsePol technique (a pulsed DNP method) is applied to selectively transfer polarization from the NV electron spin to the target ${}^{13}\text{C}$ nuclear spin, preparing it for the phase-sensitive detection sequence.
- Spin Tipping and Free Precession: A phase-controlled RF $\pi/2$ pulse (tuned to $f_{1}$) tips the polarized nuclear spin onto the XY plane, initiating free precession. This tipping step ensures the resulting precession phase ($\phi_{0}$) carries information on the nuclear spinâs azimuthal angle ($\phi$).
- Phase-Sensitive Readout: The free precession of the nuclear spin is tracked using a CP sequence combined with a novel $(\pi/2)_{y}$ readout pulse, allowing detection of the initial phase of oscillation and, consequently, unique determination of the azimuthal angle $\phi$.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD stands as the premier material and engineering partner for replicating and advancing this single-spin quantum sensing research. Our expertise in MPCVD diamond growth and precise fabrication directly addresses the critical material requirements outlined in the paper.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the isolated, high-coherence NV centers necessary for this high-resolution magnetic sensing, researchers require the highest grade of low-impurity SCD.
- Optical Grade Single Crystal Diamond (SCD): This material is critical for minimizing electronic and nuclear spin noise, enabling the long coherence times ($T_{2}^{*}$ and $T_{2}$) required by the multi-pulse CP sequence. 6CCVD specializes in ultra-low nitrogen content (Type-IIa) SCD wafers necessary for generating isolated NV centers.
- Custom Substrates: The paper utilized NV centers approximately 50 ”m below the surface. 6CCVD provides custom SCD substrates up to 10mm in thickness, allowing researchers to tune NV depth for bulk sensing studies or to access high-quality surface-layer NV centers for future single-molecule placement applications (as mentioned in the paperâs outlook).
- Isotopic Control: While the paper utilized natural abundance ${}^{13}\text{C}$ (1.1%), 6CCVD offers isotopically controlled diamond (e.g., $<0.05$% ${}^{13}\text{C}$) to create an even quieter spin environment, which is vital for improving $T_{2}$ and extending the sensing sequence duration for superior spectral and spatial resolution.
Customization Potential
Section titled âCustomization PotentialâThe experimental setup described in the paper utilized externally mounted components (copper wire, hand-wound coil). 6CCVD offers integrated fabrication services to transition these setups into robust, chip-scale quantum devices.
| Customization Service | Relevance to Research Needs | 6CCVD Capability |
|---|---|---|
| Integrated Metalization | Required for planar MW/RF striplines to generate precise local fields for spin control (PulsePol, CP, $\pi/2$ tipping pulse). | In-house deposition of Au, Pt, Pd, Ti, W, and Cu. We can pattern custom microwave/RF circuits directly onto the diamond surface. |
| High-Precision Polishing | Essential for reliable optical addressing and maintaining the quality of near-surface NV centers (for future applications). | SCD Polishing to Ra < 1 nm. PCD polishing to Ra < 5 nm (inch-size). |
| Custom Dimensions | Needed for integration into specific microscope objectives and quantum control systems. | Plates/wafers up to 125mm (PCD) and custom SCD plates with high dimensional tolerances, allowing for repeatable device mounting. |
| Laser Cutting/Etching | For forming required geometries (e.g., cantilevers, microstructures) or precisely defining regions for surface functionalization. | High-precision laser and reactive ion etching (RIE) services available. |
Engineering Support
Section titled âEngineering SupportâThe accurate determination of the spin coordinates relies on complex material properties and precise pulse sequence engineering. 6CCVDâs in-house PhD team provides specialized expertise to ensure material optimization for demanding quantum applications.
We can assist with material selection and design consultation for projects involving single-spin detection, nanoscale magnetic imaging, and other quantum processing schemes that rely on the NV centerâs exceptional coherence. This includes advising on NV creation techniques (e.g., ion implantation parameters, annealing protocols) to match specific depth requirements for future Single-Molecular NMR/MRI projects.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available) to meet your research timetable.
View Original Abstract
We report on a nanoscale quantum-sensing protocol which tracks a free precession of a single nuclear spin and is capable of estimating an azimuthal angle---a parameter which standard multipulse protocols cannot determine---of the target nucleus. Our protocol combines pulsed dynamic nuclear polarization, a phase-controlled radiofrequency pulse, and a multipulse AC sensing sequence with a modified readout pulse. Using a single nitrogen-vacancy center as a solid-state quantum sensor, we experimentally demonstrate this protocol on a single 13C nuclear spin in diamond and uniquely determine the lattice site of the target nucleus. Our result paves the way for magnetic resonance imaging at the single-molecular level.