System for the remote control and imaging of MW fields for spin manipulation in NV centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-03-16 |
| Journal | Scientific Reports |
| Authors | Giacomo Mariani, Shuhei Nomoto, Satoshi Kashiwaya, Shintaro Nomura |
| Institutions | Nagoya University, University of Tsukuba |
| Citations | 34 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis analysis summarizes a novel system for the remote control and high-resolution imaging of microwave (MW) magnetic fields utilizing Nitrogen-Vacancy (NV) centers in diamond.
- Remote MW Generation: The system uses an exchangeable gold lumped resonator, inductively coupled to a large, fixed MW planar ring antenna, eliminating the need for direct electrical connections to the resonator.
- Field Enhancement: The localized current density in the thin resonator wires achieved significant MW field enhancement, yielding a maximum Rabi frequency increase of 22 times compared to the bulk Rabi frequency generated by the planar antenna alone.
- Quantitative Imaging: Near-field MW magnetic field distribution is quantitatively mapped by measuring the Rabi oscillation frequency (Ω/2Ï) of an ensemble of near-surface NV centers via Fast Fourier Transform (FFT) imaging.
- High Resolution: The system demonstrated micrometer-scale spatial resolution, successfully imaging field confinement down to the minimum wire width of 2 ”m.
- Polarization Sensitivity: The use of a crossed-wire resonator demonstrated the systemâs capability to sense circularly polarized MW fields, which is crucial for selective spin manipulation.
- Cryogenic Advantage: The remote coupling design is highly advantageous for applications requiring cryogenic temperatures, as it minimizes heat inflow and complexity associated with wiring inside a cryostat.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Center Depth | ~10 | nm | Implantation depth from diamond surface |
| Diamond Substrate | 2.0 x 2.0 x 0.5 | mm3 | (100) CVD type IIa ultra-pure |
| Static Magnetic Field (B0) | ~4.6 | mT | Aligned along the [111] direction |
| Excitation Wavelength | 520 | nm | Pulsed laser diode |
| Maximum Rabi Frequency | 165 | MHz | Measured over the tapered-wire resonator |
| MW Field Enhancement (Max) | 22 | times | Tapered wire vs. bulk excitation |
| MW Planar Antenna Radius | 0.5 | mm | Single-loop coil for inductive coupling |
| Resonator Standoff Distance | 1.25 to 1.50 | ”m | Distance between NV layer and gold wire surface |
| Gold Film Thickness | 110 | nm | Resonator fabrication (on 10 nm Ti adhesion layer) |
| Gold Skin Depth (3.0 GHz) | 1.38 | ”m | Current density distribution context |
| Objective Lens Numerical Aperture (NA) | 0.73 | - | Used for PL collection |
| Diffraction Limit (λ ~ 700 nm) | ~480 | nm | Optical resolution limit |
| Minimum Imaging Pixel Size (N=1) | 66 | nm | CMOS camera pixel size equivalent |
Key Methodologies
Section titled âKey MethodologiesâThe experimental system integrates optical detection with high-frequency MW control for near-field imaging.
- NV Center Creation: Ultra-pure (100) CVD diamond was implanted with 15N ions (dose 2 x 1012 to 2 x 1013 cm-2) at 10 keV, followed by 800 °C annealing and acid treatment to form near-surface NV ensembles (~10 nm depth).
- Resonator Fabrication: Gold lumped resonators (straight, tapered, and crossed wires) were fabricated on a Silicon substrate using electron beam evaporation (10 nm Ti / 110 nm Au layers).
- MW Excitation and Coupling: A fixed MW planar ring antenna (0.5 mm radius) generated a uniform MW field. This field inductively coupled to the lumped resonator, which was placed approximately 0.5 mm away from the antenna.
- Optical Detection: A wide-field optical microscope setup was used. A 520 nm pulsed laser initialized the NV spins, and photoluminescence (PL) (630-800 nm) was collected via a 100x objective lens onto a cooled scientific CMOS camera.
- Rabi Oscillation Measurement: The electron spin was driven by a resonant MW pulse (TMW). The PL signal was measured for increasing TMW durations to temporally reconstruct the Rabi oscillations.
- MW Field Imaging (FFT): The Rabi frequency (Ω/2Ï), which is directly proportional to the local MW magnetic field amplitude (B+), was calculated by performing a Fast Fourier Transform (FFT) on the binned PL data for each spatial point.
- Simulation: Finite-Difference Time-Domain (FDTD) analysis was used to model the MW field distribution, approximating the planar ring antenna source as a double dipole antenna.
Commercial Applications
Section titled âCommercial ApplicationsâThe demonstrated system and methodology are highly relevant for several advanced technology sectors requiring precise control and characterization of localized electromagnetic fields.
- Quantum Information Processing (QIP):
- Enables efficient, localized driving of single or few NV spins, critical for implementing high-fidelity quantum gates and building scalable quantum registers.
- The remote coupling simplifies integration into complex quantum architectures, especially those operating at cryogenic temperatures.
- Quantum Sensing and Magnetometry:
- Provides high-resolution, quantitative imaging of magnetic fields generated by micro-scale electronic or magnetic devices.
- Useful for characterizing novel magnetic materials and studying spin dynamics in condensed matter physics.
- Microwave and RF Engineering:
- Non-invasive, near-field characterization of MW circuits, resonators, and antennas operating in the GHz regime.
- Allows mapping of field polarization (circularly polarized components) to diagnose defects and optimize device performance.
- Solid-State Physics Research:
- A versatile platform for studying coherent spin manipulation and decoherence mechanisms in solid-state defects under precisely controlled, high-amplitude MW fields.
View Original Abstract
Abstract Nitrogen-vacancy (NV) centers in diamond have been used as platforms for quantum information, magnetometry and imaging of microwave (MW) fields. The spatial distribution of the MW fields used to drive the electron spin of NV centers plays a key role for these applications. Here, we report a system for the control and characterization of MW magnetic fields used for the NV spin manipulation. The control of the MW field in the vicinity of a diamond surface is mediated by an exchangeable lumped resonator, coupled inductively to a MW planar ring antenna. The characterization of the MW fields in the near-field is performed by an FFT imaging of Rabi oscillations, by using an ensemble of NV centers. We have found that the Rabi frequency over a lumped resonator is enhanced 22 times compared to the Rabi frequency without the presence of the lumped resonator. Our system may find applications in quantum information and magnetometry where a precise and controlled spin manipulation is required, showing NV centers as good candidates for imaging MW fields and characterization of MW devices.