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 | University of Science and Technology of China, Wuhan University |
| Citations | 156 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the coherent control of nitrogen-vacancy (NV) center spins in silicon carbide (SiC) at room temperature, positioning 4H-SiC as a highly promising platform for scalable quantum technologies.
- Room Temperature Coherence: Achieved coherent control of NV center spins at 300 K, yielding a spin coherence time (T2) of approximately 17.1 ”s. This T2 value is comparable to previously studied divacancy and silicon vacancy defects in SiC.
- Telecom Emission: The NV centers exhibit fluorescence in the telecom wavelength range (1100 nm to 1420 nm), covering the O-band and E-band, which is critical for long-distance quantum communication via optical fibers.
- Concentration Optimization: Optimization of nitrogen ion implantation and annealing conditions (1050 °C for 2 hours) resulted in a six-fold increase in the NV center ensemble concentration.
- Single Photon Source: Single NV centers were generated and characterized as room-temperature photostable single-photon sources, confirmed by a second-order photon correlation function g2(0) of around 0.25.
- Scalability Advantage: The use of technologically mature and commercially available SiC materials facilitates large-scale integrated quantum photonics and the development of long-distance quantum networks.
- Dephasing Dependence: The dephasing time (T2*) was shown to decrease significantly (from 1.0 ”s to 0.45 ”s) as the nitrogen implanted dose increased from 1x1013 cm-2 to 1x1016 cm-2, highlighting the impact of lattice damage.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Platform | 4H-SiC | Crystal | Bulk high-purity epitaxy layer |
| Coherence Time (T2) | 17.1 ± 4.0 | ”s | NV ensemble, Room Temperature (300 K) |
| Dephasing Time (T2*) | 1.0 ± 0.1 | ”s | NV ensemble, Low dose (1x1013 cm-2) |
| Dephasing Time (T2*) | 0.45 | ”s | NV ensemble, High dose (1x1016 cm-2) |
| Emission Range | 1100 to 1420 | nm | Telecom wavelength (O-band and E-band) |
| Zero-Field Splitting (ZFS) | 1319.0 ± 0.1 | MHz | NV (hh) center, Room Temperature |
| Nitrogen Hyperfine Coupling (A) | ~1.3 | MHz | 14N nuclear interaction |
| Rabi Frequency | ~7.9 | MHz | Coherent spin control |
| Ion Implantation Energy | 30 | keV | Nitrogen ions (N+) |
| Implantation Depth (Shallow) | 60 | nm | SRIM simulation |
| Optimal Annealing Temperature | 1050 | °C | For maximum NV concentration |
| Optimal Annealing Time | 2 | hours | For maximum Zero Phonon Line (ZPL) intensity |
| Single Photon Purity (g2(0)) | ~0.25 | Dimensionless | Hanbury-Brown and Twiss (HBT) measurement |
| Single NV Saturation Count (Is) | 17.4 ± 0.2 | kcps | Maximal emission counts |
| Single NV Saturation Power (P0) | 1.7 ± 0.1 | mW | Excitation power |
| Fluorescence Lifetime (Ï) | 2.1 ± 0.1 | ns | Room temperature ensemble |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized ion implantation combined with nanofabrication techniques and advanced optical/microwave spectroscopy:
- Sample Base: High-purity 4H-SiC epitaxy layer was used as the base material.
- Ion Implantation: Nitrogen ions were implanted at 30 keV to create shallow NV centers (estimated depth 60 nm).
- Concentration Optimization (Ensemble): Samples were implanted with various doses (e.g., 1x1014 cm-2) and annealed at temperatures between 800 °C and 1100 °C. The optimal condition was determined to be 1050 °C for 2 hours, resulting in a six-fold concentration increase.
- Single NV Fabrication:
- A 200-nm-thick polymethyl methacrylate (PMMA) layer was deposited on the SiC surface.
- Electron-beam lithography was used to pattern 70 ± 10 nm diameter nano-aperture arrays (2 x 2 ”m2).
- Low-dose nitrogen ions (2.5x1011 cm-2) were implanted through these apertures to generate isolated single NV centers.
- Optical Excitation: A 1030 nm laser was employed for excitation, selected for its better exciting effect on NV centers and its ability to reduce background emission from divacancy defects.
- Spin Coherent Control: Optically-Detected Magnetic Resonance (ODMR) was performed using resonant microwave frequencies. Coherent control was demonstrated via Rabi oscillation, Free Induction Decay (Ramsey fringe), and Hahn echo measurements.
- Detection Systems:
- Ensemble spin control utilized a multimode fiber and a photoreceiver after a 1150 nm long pass (LP) filter.
- Single NV investigation used a single-mode fiber coupled to a superconducting single-photon detector (Scontel).
Commercial Applications
Section titled âCommercial ApplicationsâThe successful demonstration of coherent spin control and telecom emission in SiC NV centers provides a foundation for several high-value quantum technologies:
- Quantum Communication Networks: The telecom-wavelength emission (1100-1420 nm) is perfectly suited for integration into existing fiber optic infrastructure, enabling long-distance quantum key distribution (QKD) and quantum networks.
- Integrated Quantum Photonics: SiC is a technologically mature semiconductor with established wafer-scale growth and nanofabrication protocols, allowing for the scalable integration of quantum light sources and spin qubits onto a single chip.
- Distributed Quantum Computing: NV centers serve as robust, manipulatable spin qubits. SiC provides the necessary platform for constructing on-chip quantum processors that can be linked via photonic interconnects.
- High-Sensitivity Quantum Sensing: The long room-temperature coherence time (T2 = 17.1 ”s) makes these defects excellent candidates for high-sensitivity quantum metrology, including sensing of magnetic fields, electric fields, and local strain.
- Room-Temperature Single Photon Sources: The photostable single NV centers operating at room temperature are essential for generating non-classical light required in various quantum optics experiments and devices.
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.