A Fully‐Integrated Diamond Nitrogen‐Vacancy Magnetometer with Nanotesla Sensitivity
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2024-12-09 |
| Journal | Advanced Quantum Technologies |
| Authors | Yulin Dai, Wenhui Tian, Qing Liu, Bao Chen, Yushan Liu |
| Institutions | Zhejiang Lab, Zhejiang University |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study introduces a novel, fully-integrated Diamond Nitrogen-Vacancy (DNV) magnetometer specifically engineered for high-mobility applications, such as installation on Unmanned Aerial Vehicles (UAVs).
- Core Achievement: Demonstrated an optimal sensitivity of 2.14 nT/√Hz, significantly surpassing the microtesla (µT) limitations of previous fully-integrated mobile DNV systems.
- Integration and Size: Achieved full functionality integration within a compact form factor (approximately Φ 13 cm x 26 cm), ensuring low Size, Weight, and Power (SWaP).
- Custom Electronics: Successfully integrated custom-designed, high-performance components, including an FPGA-based lock-in amplifier (LIA) and a DDS-based fast microwave (MW) source, matching the performance of commercial devices in this specific setup.
- Performance Optimization: Utilized simultaneous multi-frequency MW driving (addressing hyperfine splitting) and digital balance detection to enhance the signal-to-noise ratio (SNR) by factors of 2.3 and 2.2, respectively.
- Limiting Factor: The current sensitivity is primarily limited by the electronic noise floor (2.1 nT/√Hz) of the custom 14-bit ADC and fixed-point LIA processing, rather than the photon shot noise limit (8.3 pT/√Hz).
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal Sensitivity (ηelec) | 2.14 | nT/√Hz | Achieved using digital balance detection. |
| Balanced Sensitivity (ηbal) | 3.0 | nT/√Hz | Sensitivity with digital balance detection (ENBW 10.4 Hz). |
| Unbalanced Sensitivity (ηun) | 6.6 | nT/√Hz | Sensitivity without digital balance detection. |
| Electronic Noise Floor (ηelec) | 2.1 | nT/√Hz | Noise contribution from custom electronics. |
| Photon Shot Noise Limit | 8.3 | pT/√Hz | Theoretical limit based on ODMR contrast (1.53%). |
| Form Factor (Diameter x Length) | Φ 13 x 26 | cm | Compact size suitable for UAV installation. |
| Laser Output Power (Total) | 450 | mW | Generated by high-power LD (NICHA NUGM04). |
| Laser Power on Diamond | 175 | mW | Focused power on the diamond sample. |
| Diamond Size | 1.5 x 1.5 x 0.5 | mm3 | Element Six, 100 face, 45° cut. |
| NV Concentration | 4.5 | ppm | Nitrogen-Vacancy concentration. |
| Zero-Field Splitting (D) | 2.87 | GHz | NV electronic spin ground triplet state. |
| Detection Frequency Bandwidth (ENBW) | 1.3 to 625 | Hz | Adjustable range (integration time 0.9 ms to 384 ms). |
| ADC Resolution | 14 | Bit | Dual-channel ADC (LTC2145CUP-14). |
Key Methodologies
Section titled “Key Methodologies”- Full System Integration: All essential components—high-power laser, custom MW source, integrated probe, and measurement controller—were designed and integrated into a single, compact unit (Φ13 cm x 26 cm) to achieve low SWaP suitable for mobile platforms.
- Custom Measurement Controller: An embedded system based on a Xilinx Zynq 7010 SoC (featuring an ARM Cortex-A9 processor and Artix-7 FPGA) was developed to handle signal management, data processing, and communications, implementing the lock-in amplifier (LIA) functionality digitally.
- DDS-Based Microwave Source: A custom MW source was built using an ADI AD9914 Direct Digital Synthesizer (DDS) chip, up-converted to the 2.5-3 GHz working range. This source supports fast Frequency-Shift Keying (FSK) modulation synchronized with the measurement controller.
- Multi-Frequency Driving for Hyperfine Splitting: To maximize signal strength, a 2.158 MHz modulation was applied to the output microwave via a frequency mixer. This created a triple-frequency wave that simultaneously drove all three 14N hyperfine subfeatures, resulting in a 2.3-fold SNR enhancement.
- Digital Balance Detection: A digital scheme was implemented where two photodetectors independently captured the red fluorescence signal (A) and the scattered green background light (B). The differential value was computed numerically using amplification coefficients (k1, k2) to minimize noise, yielding a 2.2-fold SNR improvement.
- Optical Probe Design: The probe utilizes a high-power 532 nm laser diode (450 mW total output) and a Compound Parabolic Concentrator (CPC) for high-efficiency collection of the red fluorescence (637-800 nm range).
Commercial Applications
Section titled “Commercial Applications”- Unmanned Aerial Vehicles (UAVs): The primary target application. The compact, low-SWaP design enables installation on small UAVs for mobile, high-precision vector magnetic sensing.
- Autonomous Navigation and Positioning: Providing precise, heading-error-free vector magnetic field data (nT-level) for enhanced autonomous navigation systems, especially in GPS-denied environments.
- Geophysical and Mineral Surveying: High-mobility magnetic mapping over large areas, offering significantly higher sensitivity than traditional mobile magnetometers for detecting subtle magnetic anomalies associated with mineral deposits.
- Quantum Sensing Hardware: The custom-developed, integrated electronics (FPGA-LIA and DDS MW source) provide a blueprint for cost-effective, compact control systems applicable to other spin-ensemble quantum sensors.
- Biomagnetism and Medical Imaging: While the current device size is large, the underlying DNV technology and optimization techniques are foundational for future miniaturized probes capable of detecting weak magnetic fields generated by biological processes (e.g., magnetoencephalography).
View Original Abstract
Abstract Ensemble diamond nitrogen‐vacancy (DNV) centers have emerged as a promising platform for precise earth‐field vector magnetic sensing, particularly in applications that require high mobility. Nevertheless, integrating all control utilities into a compact form has proven challenging, thus far limiting the sensitivity of mobile DNV magnetometers to the ‐level. This study introduces a fully integrated DNV magnetometer that encompasses all the essential components typically found in traditional platforms, while maintaining compact dimensions of approximately 13 cm 26 cm. In contrast to previous efforts, these challenges are successfully addressed by integrating a high‐power laser, a lock‐in amplifier, and a digitally‐modulated microwave source. These home‐made components show comparable performance with commercial devices under the circumstance, resulting in an optimal sensitivity approaching 2.14 nT () −1 . The limitations in this system as well as possible future improvements are discussed. This work paves the way for the use of DNV magnetometry in cost‐effective, mobile unmanned aerial vehicles, facilitating a wide range of practical applications.