Quantum sensing with nitrogen-vacancy colour centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-03-01 |
| Journal | Photoniques |
| Authors | Thierry Debuisschert |
| Institutions | Thales (France) |
| Citations | 6 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Technology: Quantum sensing utilizing Nitrogen-Vacancy (NV) color centers in diamond, which function as atomic-sized magnets capable of measuring external physical quantities with unprecedented accuracy.
- Operational Advantage: NV centers can be polarized and coherently manipulated under ambient conditions (standard laboratory environment), eliminating the need for cryostats or heavy equipment required by many competing quantum techniques.
- Measurement Principle: The system relies on Optical Detection of Magnetic Resonance (ODMR). A green laser (532 nm) pumps the NV center, and microwave radiation (near 2.87 GHz) induces spin transitions, which are read out optically via a decrease in red fluorescence (600-800 nm).
- Key Performance: The NV center measures magnetic fields by detecting the Zeeman shift in its resonance frequency, achieving nanometer-scale resolution (down to 50 nm spatial resolution in scanning magnetometry).
- Material Requirement: High-quality, ultra-pure diamond is essential, typically produced via plasma-assisted Chemical Vapor Deposition (CVD), allowing controlled doping to achieve high concentrations (few ppm) of quantum-grade NV centers.
- Versatility: Beyond magnetic fields, the technology is sensitive to pressure and temperature, making it applicable across diverse fields including spintronics, 5G communications, and advanced medical diagnostics (MRI/NMR).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Excitation Wavelength | 532 | nm | Green pump laser used for optical pumping and polarization. |
| Fluorescence Emission Range | 600-800 | nm | Stable photoluminescence (red domain) emitted by the NV center. |
| Peak Fluorescence Wavelength | 637 | nm | Specific wavelength of red fluorescence emission. |
| Zero-Field Splitting Frequency | 2.87 | GHz | Energy difference between the lowest energy spin levels (ms = 0 and ms = ±1). |
| Spatial Resolution (Magnetometry) | 50 | nm | Achieved when scanning a single NV center tip over a magnetic sample. |
| Diamond Crystal Size (CVD) | Few | mm | Typical size of large artificial diamonds produced by CVD. |
| Diamond Thickness (CVD) | Few hundred | ”m | Typical thickness of artificial diamonds. |
| Quantum Grade NV Concentration | Few | ppm | Required concentration for developing high-sensitivity sensors. |
| High Pressure Test Condition | 7 | GPa | Pressure applied in diamond anvil cells for studying material phase transitions (e.g., superconductivity). |
| Spin Polarization Gain (MRI) | 104 | Magnitude | Expected gain in efficiency for polarizing molecules used as MRI markers. |
Key Methodologies
Section titled âKey Methodologiesâ- Material Synthesis (CVD): Artificial, ultra-pure single-crystal diamond is grown using plasma-assisted Chemical Vapor Deposition (CVD) to ensure low impurity levels and controlled doping necessary for quantum applications.
- NV Center Formation: Nitrogen (N) atoms are intentionally substituted for carbon (C) atoms in the diamond lattice, adjacent to a missing carbon atom (vacancy, V), forming the negatively charged NV- center.
- Optical Polarization: The NV center is initialized into a well-defined quantum state (spin polarized) by exciting it with a green laser beam (532 nm).
- Spin Manipulation (ODMR): Microwave radiation is applied to induce resonant transitions between the ground spin states (ms = 0 and ms = ±1) at frequencies near 2.87 GHz.
- Optical Readout: The spin state is detected by monitoring the photoluminescence (red fluorescence). A resonant transition induced by the microwave field results in a measurable decrease in fluorescence intensity (Optical Detection of Magnetic Resonance).
- Magnetic Field Sensing: External magnetic fields induce a Zeeman shift, changing the resonance frequencies. By measuring the frequency difference between the split resonances, the projection of the magnetic field onto the NV axis (BNV) is determined.
- Scanning Magnetometry: A diamond tip containing a single NV center is mounted on an AFM tuning fork and scanned across a sample surface to map magnetic fields with high spatial resolution (50 nm).
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Sensing and Metrology:
- Development of high-sensitivity, miniaturized magnetometers capable of measuring both the magnitude and direction of magnetic fields.
- Sensors for measuring pressure and thermal effects by monitoring shifts in the NV centerâs resonance frequencies.
- Advanced Communications and Radar:
- NV-based spectrum analyzers developed to convert microwave frequencies into optical signals.
- Instantaneous monitoring of wide frequency bands, critical for 5G, cognitive radio, and radar applications.
- Materials Science and Spintronics:
- NV scanning magnetometry for studying magnetic structures, including antiferromagnetic domains, with unprecedented spatial resolution (50 nm).
- Monitoring material phase transitions (e.g., superconductivity) under extreme conditions (high pressure and cryogenic temperatures).
- Medical and Chemical Diagnostics:
- Functional Nuclear Magnetic Resonance (NMR) spectroscopy for chemical analysis (e.g., drug analysis) using lab-on-a-chip devices.
- Efficient polarization of molecules used as markers in Magnetic Resonance Imaging (MRI), leading to the potential manufacture of smaller and cheaper MRI machines.
- Automotive Industry:
- Magnetometers for monitoring electric current in car batteries, requiring high dynamics and sensitivity.
- Quantum Communications:
- Use of NV centers as stable single photon emitters for quantum cryptography experiments.
View Original Abstract
Quantum sensing exploits the possibility of manipulating single quantum objects and of measuring external physical quantities with unprecedented accuracy. It offers new functionalities that cannot be obtained with classical means. Quantum sensors can be based on atomic vapours, cold atoms, dopants in solid-state materials, etc. In the latter category, the nitrogen vacancy centre in diamond has received particular attention in recent years due to its very attractive characteristics.