Cavity quantum electrodynamics with color centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-08-06 |
| Journal | Optica |
| Authors | Erika Janitz, Mihir K. Bhaskar, Lilian Childress |
| Institutions | Harvard University Press, McGill University |
| Citations | 124 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond for Cavity Quantum Electrodynamics (cQED)
Section titled âTechnical Documentation & Analysis: MPCVD Diamond for Cavity Quantum Electrodynamics (cQED)âExecutive Summary
Section titled âExecutive SummaryâThis review highlights the critical role of diamond color centers in advancing quantum networking via Cavity Quantum Electrodynamics (cQED). 6CCVD provides the foundational material solutions necessary to meet the stringent requirements of this cutting-edge research.
- Core Application: Diamond defects (NV, SiV, Group-IV) serve as robust, long-lived solid-state qubits, forming coherent interfaces between optical photons and matter spins for quantum networks.
- Performance Benchmarks: State-of-the-art experiments achieved exceptional performance, including atom-photon cooperativity (C) exceeding 100 and electron spin coherence times (T2) greater than 1 ms in SiV systems.
- Material Requirement: Success hinges on ultra-high purity, electronic-grade Single Crystal Diamond (SCD) to minimize decoherence and maximize optical coherence.
- Fabrication Challenge: Both Fabry-Perot and nanophotonic approaches require ultra-thin (100 nm to 1 ”m) membranes with extremely low surface roughness (Ra ~ 0.1 nm-rms) to mitigate scattering losses.
- 6CCVD Solution: We specialize in providing custom-dimension, electronic-grade SCD wafers and membranes with industry-leading polishing (Ra < 1 nm standard, specialized post-processing available) and integrated metalization capabilities (Au, Pt, Pd) essential for scalable cQED platforms.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points extracted from the research paper define the critical parameters for high-performance diamond cQED systems.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| SiV ZPL Wavelength | 737 | nm | Negatively charged Silicon Vacancy |
| NV ZPL Wavelength | 637 | nm | Nitrogen Vacancy |
| SiV Excited State Lifetime (Ï) | 1.6 - 1.7 | ns | At 4 K |
| NV Excited State Lifetime (Ï) | 11 - 13 | ns | |
| SiV Spin Coherence (T2) | > 1 | ms | Achieved at 100 mK using CPMG sequences |
| SiV Orbital Splitting (ħÎGS/kB) | 2.4 | K | Requires operation below this temperature to reduce phonon occupation |
| Achieved Cooperativity (C) | > 100 | N/A | Nanophotonic SiV-cQED system (C >> 1 regime) |
| Required Surface Roughness (Ra) | ~ 0.1 | nm-rms | Required for ICP RIE etched membranes to minimize surface loss |
| Diamond Membrane Thickness | 100 | nm - 1 | ”m |
| High Cavity Finesse (F) | 11,000 | N/A | Achieved in open microcavity (GeV experiment) |
Key Methodologies
Section titled âKey MethodologiesâSuccessful realization of high-performance diamond cQED relies on precise material engineering and advanced nanofabrication techniques.
- High-Purity Material Growth: Utilization of electronic-grade Single Crystal Diamond (SCD) grown via MPCVD to ensure minimal native nitrogen impurities, which is crucial for achieving long spin coherence times.
- Defect Creation and Localization: Color centers (SiV, NV, GeV, SnV) are introduced via:
- Ion implantation (e.g., Si, N, Ge, Sn) using focused ion beams (FIB) or lithographically aligned masks for sub-100 nm placement accuracy.
- Subsequent high-temperature, high-vacuum annealing (often > 1200 °C) to repair lattice damage and mobilize vacancies to form the desired defect structure.
- Membrane Preparation: Fabrication of ultra-thin SCD membranes (down to 100 nm) from bulk material using techniques like laser slicing, mechanical polishing, or implantation/liftoff processes.
- Surface Planarization: Achieving atomic-scale surface smoothness (target Ra ~ 0.1 nm-rms) through Inductively Coupled Plasma Reactive Ion Etching (ICP RIE) using alternating ArCl2 and O2-based recipes to minimize optical scattering losses.
- Cavity Fabrication:
- Fabry-Perot: Bonding thin SCD membranes to highly reflective dielectric mirrors, coupled with micro-machined spherical mirrors (often on fiber tips).
- Nanophotonic: Defining high quality factor structures (Photonic Crystal Cavities, Microdisks) in bulk SCD using electron-beam lithography, dry etching, and selective crystallographic underetching.
- Spin Control Integration: Deposition of lithographically aligned metal striplines (e.g., Gold) on the cavity substrate for microwave delivery, enabling coherent spin manipulation at cryogenic temperatures.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-specification diamond materials and fabrication services required to replicate and advance the cQED research outlined in this paper.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the required optical coherence and spin properties, researchers must utilize the highest quality diamond available.
- Optical Grade Single Crystal Diamond (SCD): Essential for minimizing optical absorption and scattering losses. Our electronic-grade SCD provides the ultra-low impurity levels necessary for long spin coherence (T2) and high quantum efficiency (QE).
- Boron-Doped Diamond (BDD): Required for specific applications, such as stabilizing the neutral charge state (SiV0) or for use in integrated microwave components. 6CCVD supplies BDD with controlled doping levels.
Customization Potential
Section titled âCustomization PotentialâThe success of cQED relies on precise control over material dimensions and interfaces. 6CCVDâs capabilities directly address the critical fabrication challenges identified in the review.
| Research Requirement | 6CCVD Capability | Sales Advantage |
|---|---|---|
| Ultra-Thin Membranes (100 nm to 1 ”m) | SCD Thickness Control: We offer custom SCD plates/wafers from 0.1 ”m up to 500 ”m thickness, perfectly matching the required range for both nanophotonic films and Fabry-Perot membranes. | Enables direct fabrication of high-Q/V nanophotonic devices and bulk-like Fabry-Perot systems. |
| Ultra-Smooth Surfaces (Ra ~ 0.1 nm-rms) | Precision Polishing: Standard SCD polishing achieves Ra < 1 nm. Specialized post-processing is available to meet the Ra ~ 0.1 nm-rms requirement, minimizing surface-induced optical loss. | Critical for achieving high cavity finesse (F > 10,000) and reducing emitter spectral diffusion. |
| Scalability & Integration | Large Format Substrates: We supply PCD wafers up to 125 mm and SCD substrates up to 10 mm thick, supporting wafer-scale fabrication and parallelized device arrays. | Accelerates the transition from proof-of-concept experiments to scalable quantum network nodes. |
| Microwave Control Integration | Custom Metalization: In-house deposition of Au, Pt, Pd, Ti, W, and Cu is available for creating lithographically aligned striplines and electrodes for coherent spin control and DC Stark tuning. | Provides a single-source solution for integrated spin-photon interfaces, reducing external fabrication complexity. |
| Complex Geometries | Laser Cutting Services: We offer high-precision laser cutting for custom shapes and dimensions, facilitating the preparation of substrates for nanophotonic etching and bonding. | Ensures rapid prototyping and precise substrate preparation for complex cavity designs. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers possesses deep expertise in MPCVD diamond growth and post-processing. We can assist researchers with:
- Material Selection: Optimizing SCD purity and thickness for specific color center applications (e.g., NV vs. SiV).
- Process Optimization: Consulting on surface preparation techniques (polishing, etching) to achieve the ultra-low roughness required for high-Q nanophotonic cavities.
- Defect Integration Strategy: Advising on the optimal substrate specifications for subsequent ion implantation and high-temperature annealing processes.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Coherent interfaces between optical photons and long-lived matter qubits form a key resource for a broad range of quantum technologies. Cavity quantum electrodynamics (cQED) offers a route to achieve such an interface by enhancing interactions between cavity-confined photons and individual emitters. Over the last two decades, a promising new class of emitters based on defect centers in diamond has emerged, combining long spin coherence times with atom-like optical transitions. More recently, advances in optical resonator technologies have made it feasible to realize cQED in diamond. This article reviews progress towards coupling color centers in diamond to optical resonators, focusing on approaches compatible with quantum networks. We consider the challenges for cQED with solid-state emitters and introduce the relevant properties of diamond defect centers before examining two qualitatively different resonator designs: micrometer-scale Fabry-Perot cavities and diamond nanophotonic cavities. For each approach, we examine the underlying theory and fabrication, discuss strengths and outstanding challenges, and highlight state-of-the-art experiments.