Measurement of weak static magnetic field with nitrogen-vacancy color center
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Li Lu-Si, LI Hong-hui, Zhou Li-li, YANG Zhi-Sheng, Ai Qing |
| Citations | 7 |
| Analysis | Full AI Review Included |
Technical Analysis and Commercial Solutions: Weak Static Magnetic Field Measurement via NV Center Decoherence
Section titled âTechnical Analysis and Commercial Solutions: Weak Static Magnetic Field Measurement via NV Center DecoherenceâExecutive Summary
Section titled âExecutive SummaryâThis research explores a novel method for high-precision measurement of weak static magnetic fields ($B$) utilizing the electron spin decoherence time ($T_R$) of Nitrogen-Vacancy (NV) centers in diamond.
- Core Principle: The method leverages the extreme sensitivity of the NV center Larmor precession period ($T_R$) to the magnitude of the external magnetic field ($B$), particularly under Hahn Echo pulse sequences.
- Measurement Advantage: Unlike traditional high-sensitivity magnetometers (e.g., SQUIDs), this technique is robust for operation under ambient conditions (Room Temperature and Atmospheric Pressure), simplifying deployment for applications like geomagnetism.
- Achieved Sensitivity: Initial simulation using natural abundance 13C diamond (1.1%) yields a sensitivity of approximately 20 ”T/Hz1/2.
- Pathway to Ultra-High Sensitivity: The paper confirms that isotopic purification (reducing 13C concentration) and utilizing ensemble NV centers can significantly extend the coherence time ($T_2$), pushing the ultimate sensitivity to 60 nT/Hz1/2 or better.
- Measurement Technique: Three-dimensional (3D) field mapping is achieved by sequential $T_R$ measurements across three mutually orthogonal NV axis orientations.
- 6CCVD Value Proposition: 6CCVD provides the necessary ultra-high purity, isotopically enriched Single Crystal Diamond (SCD) material essential for maximizing $T_2$ and realizing the target 60 nT/Hz1/2 sensitivity.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Ground State Splitting ($\Delta$) | 2.87 | GHz | Zero-Field Splitting (ZFS) between $m_s=0$ and $m_s=\pm 1$ |
| Simulated Diamond Environment | 1.1 (Natural) | % | 13C abundance used for initial simulation |
| Natural Abundance $T_2$ (Simulated) | $\approx 0.5$ | ms | Coherence time limit due to 13C bath |
| Target $T_2$ Improvement Goal | $\approx 0.6$ | s | Required for optimal sensitivity (Cited Ref [34]) |
| Achieved Sensitivity (1.1% 13C) | $\approx 20$ | ”T/Hz1/2 | Single NV center performance baseline |
| Target Sensitivity (Purified 12C) | $\approx 60$ | nT/Hz1/2 | Requires 12C enrichment/low 13C concentration |
| $T_R$ vs $B$ Relationship ($\alpha$) | $T_R = 0.9366 B^{-1}$ | ms·G | Highly accurate inverse relationship used for sensing |
| $T_W$ vs $B$ Relationship | $T_W = 0.0427 B^{-0.65}$ | ms·G | Used for weak magnetic field range (1 G to 100 G) |
| Larmor Precession Period | $T_R$ | ms | The timescale used as the magnetic field âscaleâ |
| NV Main Axis Orientation | $\text{[111]}$ | Crystal Axis | Defined by the N-V bond direction |
| Operating Temperature | Room Temperature | $\text{K}$ or $^\circ\text{C}$ | Key advantage over SQUIDs |
Key Methodologies
Section titled âKey MethodologiesâThe magnetic sensing technique relies on simulating and measuring the electron spin decoherence process of the NV center under external magnetic fields ($B$) using pulse control.
- Material Basis: Utilizing the NV color center in diamond, characterized by an $S=1$ electronic ground state, which is easily initialized and read out optically (via fluorescence intensity differences between $m_s=0$ and $m_s=\pm 1$ states).
- Decoherence Mechanism: Decoherence is primarily driven by the magnetic dipole coupling between the NV electron spin and the randomly distributed nuclear spins in the diamond lattice, specifically the naturally abundant 13C nuclear spins.
- Pulse Control: The Hahn Echo (HE) microwave pulse sequence is applied to the system. This sequence partially refocuses the environmental noise, enabling the observation of three characteristic decoherence timescales: $T_W, T_R, T_2$.
- Field Sensing Metric: The Larmor precession period ($T_R$) of the nuclear spins, which modulates the electron spin coherence, is identified as having the highest responsiveness ($\partial T_R / \partial B \propto B^{-2}$) to weak magnetic field variations.
- 3D Measurement: To determine the full magnitude and direction of an unknown static field $B$, the $T_R$ measurement is performed three times, aligning the NV primary axis along three mutually orthogonal directions ($x, y, z$).
- Sensitivity Optimization: The critical pathway to reaching nano-Tesla (nT) sensitivity is the extension of the overall coherence time $T_2$. This is achieved by minimizing the concentration of 13C isotopes in the diamond host lattice via isotopic purification.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the specialized, high-purity diamond materials and processing services required to replicate this groundbreaking research and achieve the proposed ultra-high sensitivity targets.
| Requirement from Research Paper | 6CCVD Solution & Capability | Commercial Advantage |
|---|---|---|
| Ultra-Long $T_2$ (Isotopic Purification) | High Purity Optical Grade SCD with < 100 ppm Nitrogen and < 0.01% 13C (high 12C enrichment). | Enables achievement of $T_2$ coherence times in the second range, maximizing sensitivity to 60 nT/Hz1/2 or better. |
| Single Crystal Host Material | Single Crystal Diamond (SCD) Plates/Wafers up to 125mm. | Provides the defect-controlled lattice necessary for stable, high-quality NV formation and quantum coherence experiments. |
| High NV Density (Ensemble Sensing) | Custom SCD Material tailored for optimized Nitrogen doping levels and controlled NV creation via post-growth irradiation/annealing. | Increases signal-to-noise ratio ($\propto \sqrt{n}$) by utilizing an ensemble of NV centers, further boosting measurement speed and sensitivity. |
| Precise Optical Access | Precision Polishing Services: Ra < 1 nm on SCD surfaces. | Critical for high-fidelity laser initialization, microwave manipulation, and fluorescence readout required for the Hahn Echo sequences. |
| 3D Alignment Requirement | Custom Orientation Control: SCD available in precise $\text{[111]}$ or $\text{[100]}$ orientations. | Ensures the highest concentration of NV axes are aligned optimally for precise vector magnetometry. |
| Integration/Readout Support | Custom Metalization Services: In-house capability for Au, Pt, Pd, Ti, W, Cu electrode deposition. | Supports integration of microwave/RF delivery structures directly onto the diamond surface for precise pulse control. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and technical engineers specialize in optimizing CVD growth recipes to meet the stringent demands of quantum applications. We offer consultation to assist researchers in selecting the precise combination of nitrogen concentration, isotopic purity (12C enrichment), and crystal orientation necessary for similar high-resolution static weak field magnetometry projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We propose a strategy to measure weak static magnetic fields with\nnitrogen-vacancy color center in diamond. Inspired by avian magnetoreception\nmodels, we consider the feasibility of utilizing quantum coherence phenomena to\nmeasure weak static magnetic fields. Nitrogen-vacancy (NV) color centers are\nregarded as the ideal platform to study quantum sciences as a result of its\nlong coherence time up to a millisecond timescale. In high-purity diamond,\nhyperfine interaction with 13C nuclear spins dominates the decoherence process.\nIn this paper, we numerically simulate the decoherence process between 0 and +1\nof the individual NV color center spin in 13C nuclear baths with various of\nmagnitudes of external magnetic fields. By applying Hahn echo into the system,\nwe obtain the coherence of NV color center spin as a function of total\nevolution time and magnetic field. Furthermore we obtain the high-accuracy\nrelationship between the three decoherence-characteristic timescales, i.e. T_W,\nT_R, T_2, and magnetic field B. And we draw a conclusion that T_R has the\nhighest sensitivity about magnetic field among the three time-scales. Thus, for\na certain NV color center, T_R can be the scale for the magnitude of magnetic\nfield, or rather, the component along the NV electronic spin axis. When\nmeasuring an unknown magnetic field, we adjust the NV axis to three mutually\northogonal directions respectively. By this means, we obtain the three\ncomponents of the magnetic field and thus the magnitude and direction of the\nactual magnetic field. The accuracy could reach 60 nT/Hz^{1/2},and could be\ngreatly improved by using an ensemble of NV color centers or diamond crystals\npurified with 12C atoms.\n