Level anti-crossings of a nitrogen-vacancy center in diamond - decoherence-free subspaces and 3D sensors of microwave magnetic fields
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-10-01 |
| Journal | New Journal of Physics |
| Authors | K Rama Koteswara Rao, Dieter Suter |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Decoherence-Free NV Centers in MPCVD Diamond
Section titled âTechnical Documentation & Analysis: Decoherence-Free NV Centers in MPCVD DiamondâReference Paper: K. Rama Koteswara Rao and Dieter Suter, âLevel anti-crossings of an NV center in diamond: Decoherence-free subspaces and 3D sensors of microwave magnetic fieldsâ (arXiv:1908.07796v1, 2019).
Executive Summary
Section titled âExecutive SummaryâThis research successfully leverages the physics of Nitrogen-Vacancy (NV) center Level Anti-Crossings (LACs) in diamond coupled to first-shell 13C nuclear spins to achieve significant improvements in quantum coherence and demonstrate advanced vector magnetometry.
- Core Achievement: Observation of decoherence-free subspaces (DFS) at specific static magnetic field orientations ($\theta \approx 38.4^\circ$ and $\theta = 90^\circ$).
- Coherence Enhancement: Electron spin coherence times (T2*) were extended by factors of 5 to 7, reaching up to 10.5 ”s, due to the Zero First-Order Zeeman (ZEFOZ) shift effect.
- Application Demonstrated: Vector detection of microwave (MW) magnetic fields using a single NV center by analyzing transition amplitudes at the LAC points.
- Material Requirement: The study necessitates ultra-high purity diamond (substitutional nitrogen concentration < 5 ppb) to ensure the spin bath is dominated by 13C nuclear spins, maximizing T2*.
- Methodology: Precise 3D orientation of a small static magnetic field (B = 28.9 G) was critical, coupled with Optically Detected Electron Spin Resonance (ESR) and Ramsey Free Induction Decay (FID) sequences.
- 6CCVD Value Proposition: 6CCVD specializes in providing the requisite high-purity Single Crystal Diamond (SCD) substrates, custom dimensions, and metalization necessary to replicate and advance this critical quantum sensing research.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research, highlighting the critical performance metrics achieved at the Level Anti-Crossings (LACs).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Static Magnetic Field (B) | 28.9 | G | Field strength used to induce LACs |
| Electron Spin Coherence Time (T2*) (Baseline) | 1.6 | ”s | Measured at arbitrary B orientation (No LAC) |
| Electron Spin Coherence Time (T2*) (Maximum DFS) | 10.5 | ”s | Achieved for Transition 1 at $\theta \approx 38.4^\circ$ LAC |
| Coherence Time Improvement | 5 to 7 | Times | Factor increase due to ZEFOZ shift at LACs |
| Critical Polar Angle ($\theta$) (LAC I) | 38.4 | ° | Where 2$\gamma_e$B cos $\theta$ equals 13C hyperfine splitting ($\approx 127$ MHz) |
| Critical Polar Angle ($\theta$) (LAC II) | 90 | ° | Transverse plane orientation |
| Substitutional Nitrogen Purity | < 5 | ppb | Required concentration for ultrapure diamond |
| Electron Spin Zero-Field Splitting (D) | 2.87 | GHz | Intrinsic NV property |
| 13C Hyperfine Coupling (A1zz) | 128.9 | MHz | First-shell nuclear spin coupling |
| MW Field Amplitude (Bmw) | 0.31 | G | Determined via vector detection scheme |
| RF Field Amplitude (Brf) | 0.12 | G | Determined via vector detection scheme |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success relied on precise material selection and highly controlled magnetic and microwave environments.
- Material Preparation: Utilized natural-abundance 13C diamond with extremely low substitutional nitrogen concentration (< 5 ppb) to minimize the electron spin bath and isolate the NV-13C system.
- MW Field Generation: Microwave (MW) fields were generated using a 20 ”m thin wire attached directly to the diamond surface, requiring high surface quality and integration capability.
- Magnetic Field Control: A permanent magnet attached to two rotational stages provided precise 3D control over the static magnetic field orientation (B = 28.9 G) relative to the NV axis.
- Coherence Measurement: Optically Detected Electron Spin Resonance (ESR) spectra were measured using the Ramsey pulse sequence (Free Induction Decay, FID) to quantify T2* coherence times.
- Vector Detection: The azimuthal ($\eta$) and polar ($\zeta$) angles of the MW magnetic field were determined by measuring the relative amplitudes ($I_a$) of the four electron spin transitions (1-4) at the LAC point, exploiting the dominance of single magnetic dipole moment components.
- Azimuthal Angle Determination: Calculated using the ratio of transition amplitudes: $\vert \tan \eta \vert = \sqrt{I_1 / I_2} = \sqrt{I_3 / I_4}$.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the foundational material science and engineering services required to replicate, optimize, and scale the advanced quantum sensing and control techniques demonstrated in this research.
Applicable Materials for Quantum Coherence
Section titled âApplicable Materials for Quantum CoherenceâTo achieve the observed 5-7x extension in T2* coherence time, the starting material must be of exceptional purity and crystalline quality.
| Material Requirement | 6CCVD Material Solution | Technical Rationale |
|---|---|---|
| Ultra-Low Nitrogen Concentration (N < 5 ppb) | Optical Grade Single Crystal Diamond (SCD) | Our MPCVD process ensures extremely low substitutional nitrogen, minimizing the primary source of electron spin bath decoherence. |
| Controlled 13C Environment | Custom Isotope Control (Natural or Enriched) | We offer SCD substrates with natural 13C abundance (as used in this study) or isotopically enriched 12C (> 99.99%) for applications requiring minimal nuclear spin noise. |
| High Crystalline Quality | High-Purity SCD Wafers | Minimizes lattice defects and strain, which are critical for maintaining the precise energy level structure required for stable LAC operation. |
Customization Potential for Advanced Integration
Section titled âCustomization Potential for Advanced IntegrationâThe experiment required integrating a 20 ”m wire for MW delivery, emphasizing the need for high-precision material preparation.
| Research Requirement | 6CCVD Customization Service | Specification Match |
|---|---|---|
| Substrate Dimensions | Custom Plate/Wafer Sizing | SCD thickness from 0.1 ”m up to 500 ”m. PCD wafers up to 125mm diameter. |
| Surface Preparation | Precision Polishing | Ultra-low roughness polishing (Ra < 1nm for SCD) ensures optimal contact and minimizes surface-related decoherence. |
| MW Circuit Integration | Custom Metalization | Internal capability to deposit Au, Pt, Pd, Ti, W, and Cu films, enabling the fabrication of on-chip transmission lines, waveguides, or contact pads for enhanced MW/RF field delivery and vector control. |
Engineering Support & Application Extension
Section titled âEngineering Support & Application ExtensionâThis research demonstrates a powerful technique for vector microwave magnetometry and precise quantum control. 6CCVDâs expertise directly supports the next generation of these projects.
- Vector Magnetometry: Our in-house PhD team can assist researchers in selecting the optimal SCD material specifications (purity, orientation, and thickness) required to maximize the sensitivity and spatial resolution of single-spin vector detection schemes.
- Optimal Control Techniques: The paper notes that precise knowledge of the MW Hamiltonian (including orientation) is crucial for optimal control. 6CCVD materials provide the stable, high-coherence platform necessary for implementing complex pulse sequences (e.g., dynamical decoupling) that rely on accurate field calibration.
- Global Supply Chain: We offer reliable global shipping (DDU default, DDP available) to ensure rapid delivery of custom-engineered diamond substrates worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Nitrogen-vacancy (NV) centers in diamond have become an important tool for quantum technologies. All of these applications rely on long coherence times of electron and nuclear spins associated with these centers. Here, we study the energy level anti-crossings of an NV center in diamond coupled to a first-shell 13 C nuclear spin in a small static magnetic field. These level anti-crossings (LACs) occur for specific orientations of the static magnetic field due to the strong non-secular components of the Hamiltonian. At these orientations we observe decoherence-free subspaces, where the electron spin coherence times ( <mml:math xmlns:mml=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ overflow=âscrollâ> <mml:msubsup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> ) are 5-7 times longer than those at other orientations. Another interesting property at these LACs is that individual transition amplitudes are dominated by a single component of the magnetic dipole moment. Accordingly, this can be used for vector detection of microwave magnetic fields with a single NV center. This is particularly important to precisely control the center using numerical optimal control techniques.