Study of coherent population trapping and AC Stark effect in ensembles of NV-centers in diamond at room temperature in microwave range
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-01-01 |
| Journal | Оптика и спектроскопия |
| Authors | Р. А. Ахмеджанов, Л. А. Гущин, I. V. Zelensky, Mitrofanova T.G., В. А. Низов |
| Institutions | Kazan Scientific Center, Institute of Applied Physics |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: NV-Center Coherence in MPCVD Diamond
Section titled “Technical Documentation & Analysis: NV-Center Coherence in MPCVD Diamond”This document analyzes the research paper “Study of coherent population trapping and AC Stark effect in ensembles of NV-centers in diamond at room temperature in microwave range.” It extracts critical technical data and maps the material requirements directly to 6CCVD’s advanced MPCVD diamond capabilities, positioning our products as the ideal solution for replicating and advancing this quantum research.
Executive Summary
Section titled “Executive Summary”The study successfully demonstrated key quantum interference phenomena—Coherent Population Trapping (CPT) and the AC Stark (Autler-Townes) effect—using ensembles of Nitrogen-Vacancy (NV) centers in diamond at room temperature.
- Core Achievement: Observation of CPT and AC Stark effects via microwave transitions between ground state spin sublevels, utilizing the Optically Detectable Magnetic Resonance (ODMR) method.
- A-Scheme Implementation: The experiment required applying a small, angled external magnetic field (~35 G) to mix electron and nuclear spins, thereby lifting the nuclear spin projection ban necessary to form the three-level $\Lambda$-scheme.
- Material Requirement: The research relied on a high-purity, low-concentration CVD diamond layer (7 µm thick, 1014 cm-3 NV concentration) to minimize lattice defects and achieve narrow resonance features.
- Performance Limitation: The measured CPT resonance width was approximately 200 kHz, indicating significant decoherence rates, which highlights the critical need for ultra-high-quality, electronic-grade Single Crystal Diamond (SCD) to extend coherence times (T2).
- Methodology: High-power microwave radiation (up to 16 W) was delivered via a 3 mm loop antenna, and optical pumping was achieved using a 532 nm laser in a confocal microscopy setup.
- 6CCVD Value Proposition: 6CCVD specializes in providing the high-purity SCD substrates and custom thin-film growth necessary to reduce decoherence and improve the fidelity of quantum sensing and computing applications based on NV centers.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the experimental section of the paper:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Layer Thickness | 7 | µm | CVD layer grown on HPHT substrate |
| NV-Center Concentration | ~1014 | cm-3 | Estimated low concentration |
| Experiment Temperature | Room | °C | All measurements conducted at ambient temperature |
| Ground State Splitting (D) | 2.88 | GHz | Zero-field splitting of electron spin sublevels |
| Nuclear Spin Splitting (Q) | 4.95 | MHz | Used to define the lower levels of the A-scheme |
| External Magnetic Field (B) | ~35 | G | Applied at ~75° to the NV axis for spin mixing |
| Optical Pumping Wavelength | 532 | nm | Pump laser used for spin polarization |
| Optical Spot Diameter | ~100 | µm | Focal spot size on the sample surface |
| Microwave Amplifier Power | Up to 16 | W | Maximum power supplied to the antenna |
| Estimated Rabi Frequency (CPT) | 10-15 | kHz | Rabi frequency for the weak, nuclear spin-changing transitions |
| Estimated Rabi Frequency (AC Stark) | ~3 | MHz | Equivalent Rabi frequency for 0 dBm generator output |
| Measured CPT Resonance Width | ~200 | kHz | Determined by the relaxation rate between lower levels |
Key Methodologies
Section titled “Key Methodologies”The experiment utilized a combination of high-purity diamond material, precise magnetic field control, and high-power microwave delivery in a confocal ODMR setup.
- Material Growth: A 7 µm layer of CVD diamond with a low concentration of NV-centers (1014 cm-3) was grown on an HPHT substrate.
- Confocal ODMR Setup: Fluorescence was collected using a confocal microscopy configuration. A 532 nm laser was used for optical pumping, and a photomultiplier tube (PMT) registered the spin-dependent fluorescence signal.
- Magnetic Field Alignment: An external magnetic field (~35 G) was applied via a coil, oriented at a large angle (~75°) to the central group of NV-centers, enabling transitions that change the nuclear spin projection.
- Microwave Delivery: A 3 mm diameter loop antenna, pressed against the sample surface, delivered the microwave fields. Two generators were combined to provide the probe and drive fields necessary for two-photon CPT and AC Stark measurements.
- CPT Observation: The probe field scanned the nuclear spin-changing transition, while the drive field was tuned to the adjacent main transition. CPT was observed as a narrow dip in the fluorescence profile when the two-photon detuning matched the ground state splitting.
- AC Stark Effect Observation: The drive field was tuned off-resonant or through resonance with the electron spin transitions to observe the resulting shifts and splitting (Autler-Townes effect) in the ODMR profile.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research demonstrates the critical role of high-quality diamond material in achieving and controlling quantum coherence phenomena. The observed CPT linewidth of 200 kHz suggests that material quality (specifically, lattice defects and residual nitrogen) remains the primary limiting factor for achieving longer coherence times (T2).
6CCVD is uniquely positioned to supply the next generation of materials required to push these quantum limits.
Applicable Materials
Section titled “Applicable Materials”To replicate and significantly improve the results of this study, researchers require diamond with superior purity and precise doping control:
| Research Requirement | 6CCVD Material Recommendation | Technical Rationale |
|---|---|---|
| Low Decoherence / Narrow Linewidth | Electronic Grade Single Crystal Diamond (SCD) | Ultra-low defect density (low [N] and [B]) is essential to minimize spin bath noise and reduce the 200 kHz CPT linewidth, maximizing T2 coherence time. |
| Controlled NV Ensemble | Custom Nitrogen-Doped SCD | We offer precise, controlled nitrogen incorporation during MPCVD growth, allowing optimization of the NV concentration (e.g., targeting 1014 cm-3 or lower) for maximum ODMR contrast and minimal spin-spin interaction. |
| High-Power Microwave Interaction | High-Purity Polycrystalline Diamond (PCD) | For applications requiring larger area coverage (up to 125 mm) or robust thermal management under high microwave power (up to 16 W), our PCD offers exceptional thermal conductivity. |
Customization Potential
Section titled “Customization Potential”The experimental setup utilized specific geometries and required high-quality interfaces. 6CCVD offers comprehensive customization services to meet these exact engineering needs:
- Custom Dimensions and Thickness: The paper used a 7 µm layer. 6CCVD provides SCD and PCD plates/wafers with custom thicknesses ranging from 0.1 µm up to 500 µm for active layers, and substrates up to 10 mm for robust handling. We can supply wafers up to 125 mm in diameter (PCD).
- Precision Polishing: To ensure minimal scattering losses for the 532 nm pump laser and optimal coupling for the 3 mm loop antenna, 6CCVD guarantees SCD surface roughness Ra < 1 nm and inch-size PCD roughness Ra < 5 nm.
- Integrated Antenna Structures: The experiment required a microwave antenna pressed against the surface. 6CCVD offers in-house metalization services (Au, Pt, Pd, Ti, W, Cu), allowing researchers to integrate patterned microwave transmission lines or contact pads directly onto the diamond surface for superior coupling efficiency and reliability.
- Laser Cutting and Shaping: We provide custom laser cutting services to achieve unique sample geometries required for integration into specialized quantum setups.
Engineering Support
Section titled “Engineering Support”The successful implementation of the A-scheme for CPT relies heavily on precise material selection and understanding the interaction between lattice defects and spin dynamics. 6CCVD’s in-house PhD team specializes in the physics of NV centers and can assist with material selection for similar Quantum Sensing and Coherence projects, ensuring optimal purity and doping profiles for achieving record T2 times.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We study coherent population trapping and AC Stark effect using microwave transitions between the sublevels of the ground state of the NV-center. Sublevels with different projections of the nuclear spin of the nitrogen atom are used to implement the -scheme. Dependence of the characteristics of the coherent population trapping dip on the control field frequency and intensity is studied. Various schemes for observing the AC Stark effect are considered. Keywords: NV-center, coherent population trapping, AC Stark.