Coherent Control of Nitrogen-Vacancy Center Spins in Silicon Carbide at Room Temperature
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-06-01 |
| Journal | Physical Review Letters |
| Authors | Junfeng Wang, FeiâFei Yan, Qiang Li, Zhenghao Liu, He Liu |
| Institutions | Wuhan University, University of Science and Technology of China |
| Citations | 156 |
| Analysis | Full AI Review Included |
Technical Analysis: Coherent Control of Nitrogen-Vacancy Center Spins in Silicon Carbide
Section titled âTechnical Analysis: Coherent Control of Nitrogen-Vacancy Center Spins in Silicon CarbideâThis document analyzes the research detailing the coherent control of Nitrogen-Vacancy (NV) center spins in 4H-SiC at room temperature. While the research focuses on Silicon Carbide (SiC) as an alternative quantum platform, 6CCVD leverages its expertise in MPCVD diamond to offer superior material solutions for quantum information processing, particularly where intrinsic spin coherence and advanced fabrication are critical.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated coherent control of Nitrogen-Vacancy (NV) center spins in 4H-SiC at room temperature, achieving a spin coherence time (T2) of 17.1 ”s.
- Telecom Emission: The NV centers exhibit fluorescence in the telecom range (1100 nm to 1420 nm), addressing a key limitation of traditional diamond NV centers (visible emission).
- Scalability & Concentration: NV center concentration was increased six-fold through optimized annealing conditions (1050 °C for 2 hours) in bulk high-purity 4H-SiC epitaxy layers.
- Single Photon Source: Single NV centers were generated using electron-beam lithography and ion implantation, demonstrating photostable single photon emission with a saturation count rate of 17.4 kcps.
- Material Comparison: SiC is promoted for its mature nanofabrication and telecom emission. However, 6CCVDâs Electronic Grade Single Crystal Diamond (SCD) offers intrinsic T2 coherence times orders of magnitude greater (milliseconds vs. 17.1 ”s), which is essential for complex quantum computation.
- 6CCVD Value Proposition: 6CCVD provides high-purity SCD and large-area PCD substrates (up to 125mm) with advanced polishing (Ra < 1 nm) and custom metalization, directly addressing the scalability and integration requirements of large-scale quantum networks.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the analysis of the NV center ensemble and single defects in 4H-SiC:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Spin Coherence Time (T2) | 17.1 ± 4.0 | ”s | Room Temperature (Hahn Echo) |
| Spin Dephasing Time (T2*) | 1.0 ± 0.1 | ”s | Room Temperature (Ramsey Fringe, 350 G) |
| Zero-Field Splitting (ZFS) | 1319.0 ± 0.1 | MHz | Room Temperature (NV center hh ensemble) |
| Nitrogen Hyperfine Coupling (A) | 1.3 | MHz | Observed splitting at 20 K and 300 K |
| Rabi Frequency | 7.9 | MHz | Coherent control demonstration |
| Implantation Energy | 30 | keV | Nitrogen ions (N+) |
| Implantation Depth (SRIM) | 60 | nm | Shallow NV centers |
| Optimal Annealing Temperature | 1050 | °C | For 6x concentration increase |
| Optimal Annealing Time | 2 | hours | For optimal ZPL intensity |
| Single NV Saturation Count (Is) | 17.4 ± 0.2 | kcps | Single photon source |
| Single NV Saturation Power (P0) | 1.7 ± 0.1 | mW | 1030 nm excitation |
| Single NV Lifetime (Ï1) | 2.4 | ns | Excited state lifetime |
| Single NV Lifetime (Ï2) | 450 | ns | Metastable state lifetime |
Key Methodologies
Section titled âKey MethodologiesâThe generation and coherent control of NV centers in 4H-SiC relied on precise material processing and advanced optical/microwave techniques:
- Substrate Preparation: A bulk high-purity 4H-SiC epitaxy layer sample was utilized.
- Defect Generation (Ensemble): Nitrogen ions were implanted at 30 keV to create shallow NV centers (60 nm depth). Doses ranged up to 1 Ă 1016 cm-2.
- Defect Generation (Single NV Array):
- A 200-nm-thick Polymethyl Methacrylate (PMMA) layer was deposited on the SiC surface.
- Electron-Beam Lithography (EBL) was used to define 70 ± 10 nm diameter nano-aperture arrays (2 à 2 ”m2).
- Low-dose nitrogen implantation (2.5 Ă 1011 cm-2) was performed through the apertures.
- Defect Activation: Samples were subjected to high-temperature thermal annealing, with optimal conditions determined to be 1050 °C for 2 hours, resulting in a six-fold increase in NV concentration.
- Optical Excitation: A 1030 nm laser was used for pumping to selectively excite NV centers and minimize background emission from divacancy defects.
- Spin Control: Optically-Detected Magnetic Resonance (ODMR) was performed using a homebuilt confocal setup, high N.A. oil objective (1.3 N.A.), and a 1150 nm Long Pass (LP) filter to isolate the telecom emission.
- Coherence Measurement: Standard pulse sequences (Rabi oscillation, Ramsey fringe, Hahn echo) were employed using resonant microwave frequencies (e.g., 742.3 MHz at 206 Gauss) to measure T2 and T2*.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the need for materials that combine long spin coherence with mature, scalable fabrication techniques for integrated quantum photonics. While SiC offers telecom emission, its room-temperature coherence time (17.1 ”s) is fundamentally limited compared to diamond. 6CCVD provides MPCVD diamond solutions that offer superior intrinsic quantum properties alongside the necessary engineering maturity.
Applicable Materials for Quantum Information Processing
Section titled âApplicable Materials for Quantum Information ProcessingâTo replicate or extend this research with maximum performance, 6CCVD recommends:
| Material Grade | Application Focus | Key 6CCVD Specification | Advantage over SiC |
|---|---|---|---|
| Electronic Grade SCD | High-Fidelity Qubit Operation, Sensing | Ultra-low [N] and [B] impurities. Thickness: 0.1 ”m - 500 ”m. | Intrinsic T2 coherence times are typically 100x to 1000x longer (milliseconds) than the 17.1 ”s achieved in SiC. |
| Optical Grade SCD | Integrated Quantum Photonics, Waveguides | High transmission across visible and infrared spectrums. Ra < 1 nm polishing. | Superior surface quality minimizes scattering losses, critical for coupling telecom-band photons into integrated circuits. |
| High-Purity PCD | Large-Scale Wafer Processing, Heat Sinks | Plates up to 125 mm diameter. Thickness up to 500 ”m. | Provides the large-area, wafer-scale platform required for âtechnologically matureâ integrated quantum photonics, matching SiCâs scalability claims. |
Customization Potential for Integrated Devices
Section titled âCustomization Potential for Integrated DevicesâThe SiC experiment required precise defect generation (60 nm depth) and relied on external lithography and detection systems. 6CCVD offers integrated solutions to streamline device fabrication:
- Custom Dimensions and Thickness: We supply SCD and PCD plates up to 125 mm diameter, allowing for wafer-scale processing necessary for large-scale integrated quantum photonics. We can provide thin SCD films (down to 0.1 ”m) for precise shallow NV generation via implantation, matching the 60 nm depth requirement cited in the paper.
- Advanced Surface Engineering: The paper requires high-quality surfaces for integration. 6CCVD guarantees Ra < 1 nm polishing for SCD and Ra < 5 nm for inch-size PCD, ensuring optimal coupling efficiency for on-chip components.
- In-House Metalization: The ODMR and Rabi control experiments require microwave antennas. 6CCVD offers internal metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu deposition, enabling the direct fabrication of microwave transmission lines and electrodes onto the diamond substrate. This eliminates external processing steps and ensures material compatibility.
- Defect Engineering Support: While the paper used nitrogen implantation, 6CCVDâs expertise extends to in-situ growth of NV centers and optimized annealing recipes to maximize the yield and quality of specific defect types (e.g., N-V- or SiV).
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in defect engineering and quantum material science. We can assist researchers and engineers with:
- Material Selection: Choosing the optimal diamond grade (SCD vs. PCD) and orientation for specific quantum applications (e.g., high T2 vs. high thermal conductivity).
- Implantation Recipe Optimization: Tailoring ion implantation parameters (energy, dose, annealing temperature) to maximize the yield of high-quality NV centers for quantum photonics and long-distance quantum networks.
- Integrated Device Design: Consulting on the integration of microwave structures and optical elements onto diamond substrates using our custom metalization and polishing services.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Solid-state color centers with manipulatable spin qubits and telecom-ranged fluorescence are ideal platforms for quantum communications and distributed quantum computations. In this work, we coherently control the nitrogen-vacancy (NV) center spins in silicon carbide at room temperature, in which telecom-wavelength emission is detected. We increase the NV concentration sixfold through optimization of implantation conditions. Hence, coherent control of NV center spins is achieved at room temperature, and the coherence time T_{2} can be reached to around 17.1 ÎŒs. Furthermore, an investigation of fluorescence properties of single NV centers shows that they are room-temperature photostable single-photon sources at telecom range. Taking advantage of technologically mature materials, the experiment demonstrates that the NV centers in silicon carbide are promising platforms for large-scale integrated quantum photonics and long-distance quantum networks.