Hybrid Quantum Photonics Based on Artificial Atoms Placed Inside One Hole of a Photonic Crystal Cavity
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-08-17 |
| Journal | ACS Photonics |
| Authors | Konstantin G. Fehler, Lukas Antoniuk, Niklas Lettner, Anna P. Ovvyan, Richard Waltrich |
| Institutions | Centre National de la Recherche Scientifique, Institute for High Pressure Physics |
| Citations | 21 |
| Analysis | Full AI Review Included |
Hybrid Quantum Photonics: SiV- Centers in Nanodiamonds Coupled to Photonic Crystal Cavities
Section titled âHybrid Quantum Photonics: SiV- Centers in Nanodiamonds Coupled to Photonic Crystal CavitiesâThis technical documentation analyzes the research detailing the successful integration of Silicon-Vacancy (SiV-) centers in nanodiamonds (NDs) with a Silicon Nitride (Si3N4) Photonic Crystal Cavity (PCC). This work demonstrates a critical step toward high-bandwidth quantum network nodes, a key application area where 6CCVDâs high-purity MPCVD diamond materials offer superior performance and integration potential.
Executive Summary
Section titled âExecutive SummaryâThe following points summarize the core technical achievements and the resulting value proposition for high-speed quantum communication:
- High-Efficiency Quantum Node: A hybrid quantum photonic interface was realized by deterministically placing SiV- containing nanodiamonds inside a Si3N4 Photonic Crystal Cavity (PCC).
- Significant Purcell Enhancement: The coupling achieved a spontaneous emission (SE) rate enhancement, resulting in a dramatic shortening of the excited state lifetime.
- Record Bandwidth Potential: The measured lifetime was reduced to below 460 ps, which implies a potential operational bandwidth exceeding 1 GHz.
- Photon Flux Boost: The resulting coupled photon flux was enhanced by more than a factor of 14 compared to free-space emission.
- Advanced Integration Methodology: The system relies on AFM-based nanomanipulation (âpick and placeâ) to achieve highly accurate spatial positioning of the SiV- emitter within the electric field maximum of the PCC hole.
- Spectral Tuning Control: Cryogenic operation (â 2.5 K) combined with gas freezing allowed for controlled, time-resolved tuning of the cavity resonance frequency to match the SiV- Zero Phonon Line (ZPL).
Technical Specifications
Section titled âTechnical SpecificationsâThe following table extracts key quantitative data points achieved in the research, demonstrating the performance metrics of the hybrid quantum system.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Photon Flux Enhancement | > 14 | Factor | Compared to free-space emission |
| Shortened Lifetime (Ïon) | 460 | ps | Minimum measured lifetime due to Purcell effect |
| Potential Operational Bandwidth | > 1 | GHz | Implied by shortened lifetime |
| Operating Temperature | â 2.5 | K | Continuous flow-cryostat operation |
| SiV- ZPL Wavelength | â 736.2 | nm | Target transition frequency |
| Nanodiamond (ND) Size | 3 - 5 | nm | Detonation ultra-nanosized |
| Diamond Refractive Index (nDia) | 2.4 | N/A | Host material index |
| Si3N4 Refractive Index (nSi3N4) | â 2.0 | N/A | PCC waveguide material index |
| Si3N4 Film Thickness | 200 | nm | Thickness of the freestanding PCC layer |
| PCC Period (a) | 265 | nm | Bragg mirror hole separation |
| HPHT Synthesis Pressure | 8.0 | GPa | For SiV- ND fabrication |
| HPHT Synthesis Temperature | 1450 | °C | For SiV- ND fabrication |
Key Methodologies
Section titled âKey MethodologiesâThe experiment successfully combined advanced material synthesis, nanofabrication, and precision manipulation techniques.
- SiV- Nanodiamond Synthesis:
- Nanodiamonds containing SiV- centers were produced using High-Pressure High-Temperature (HPHT) synthesis.
- Recipe parameters included 8.0 GPa pressure and 1450 °C temperature, utilizing a hydrocarbon metal catalyst-free growth system with an initial atomic Si/C ratio of 1/100.
- Photonic Crystal Cavity (PCC) Fabrication:
- PCC devices were fabricated on Silicon nitride-on-insulator wafers (200 nm stoichiometric Si3N4 on 2 ”m SiO2/Si).
- Patterning utilized electron-beam lithography and CHF3/O2 plasma dry etching.
- Freestanding Structure Creation:
- The underlying SiO2 layer was removed via wet etching using hydrofluoric acid (HF) to create a freestanding Si3N4 waveguide, maximizing refractive index contrast and minimizing substrate loss.
- Deterministic Emitter Placement:
- A modified âpick and placeâ procedure was used, involving AFM-based nanomanipulation of a pre-characterized single ND using a platinum-coated cantilever tip.
- The ND was accurately positioned inside the second hole of the PCC Bragg mirror.
- Cryogenic Spectral Tuning:
- The device was cooled to approximately 2.5 K in a continuous flow-cryostat.
- Residual gas freezing was exploited to continuously shift the effective refractive index of the PCC, enabling controlled tuning of the cavity resonance wavelength (734 nm to 738 nm) into spectral overlap with the SiV- ZPL.
- Optical Characterization:
- Off-resonant continuous wave (710 nm) or pulsed (695 nm OPO) excitation was used.
- Emission was collected via integrated grating couplers and spectrally filtered (FWHM â 60 GHz) to isolate individual SiV- transitions.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for ultra-high-quality diamond materials and precision fabrication capabilities to advance solid-state quantum systems. 6CCVD is uniquely positioned to supply the foundational materials required to replicate this work and transition to next-generation, all-diamond integrated quantum circuits.
Applicable Materials for Quantum Photonics
Section titled âApplicable Materials for Quantum Photonicsâ| Research Requirement | 6CCVD Material Recommendation | Technical Rationale & Advantage |
|---|---|---|
| High-Purity Host Material (For SiV- creation) | Optical Grade Single Crystal Diamond (SCD) | Essential for creating stable, high-coherence SiV- centers via implantation or in-situ growth. Our SCD features ultra-low impurity levels (Type IIa), minimizing decoherence. |
| Integrated Photonic Circuits (Transitioning from hybrid Si3N4 to all-diamond) | Custom SCD Wafers (up to 500 ”m thick) | Provides the highest refractive index contrast (n=2.4) and thermal stability for all-diamond Photonic Crystal Cavities (PCCs), eliminating the complexity and loss associated with hybrid platforms. |
| Electrical Control & Readout (Future quantum network nodes) | Boron-Doped Diamond (BDD) | Available in both SCD and PCD formats, BDD allows for integrated electrical gates and contacts necessary for charge state control and efficient qubit readout, crucial for scalable quantum networks. |
Customization Potential & Engineering Support
Section titled âCustomization Potential & Engineering Supportâ6CCVD offers specialized services that directly address the stringent requirements of quantum device fabrication:
- Precision Substrate Dimensions: While the paper used a Si3N4 platform, 6CCVD supplies SCD and PCD plates/wafers up to 125 mm in size, enabling large-scale integration projects. We provide custom thickness control for SCD films from 0.1 ”m up to 500 ”m, matching the precise film requirements for advanced lithography.
- Ultra-Smooth Surface Quality: The deterministic AFM nanomanipulation and high-Q cavity performance demand exceptional surface finish. 6CCVD guarantees industry-leading polishing:
- SCD: Surface roughness (Ra) < 1 nm.
- Inch-size PCD: Surface roughness (Ra) < 5 nm.
- Integrated Metalization Services: For implementing the electrical control and readout mechanisms required in future quantum nodes, 6CCVD offers in-house metalization capabilities, including deposition of Au, Pt, Pd, Ti, W, and Cu.
- Global Supply Chain: We ensure reliable, global shipping (DDU default, DDP available) of sensitive materials to research facilities worldwide.
Engineering Support: 6CCVDâs in-house PhD team, specializing in MPCVD diamond growth and defect engineering, is available to assist researchers with material selection, defect creation strategies (e.g., SiV- implantation), and optimizing diamond specifications for high-bandwidth quantum network node projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Spin-based quantum photonics promise to realize distributed quantum computing\nand quantum networks. The performance depends on efficient entanglement\ndistribution, where the efficiency can be boosted by means of cavity quantum\nelectrodynamics. The central challenge is the development of compact devices\nwith large spin-photon coupling rates and high operation bandwidth. Photonic\ncrystal cavities comprise strong field confinement but put high demands on\naccurate positioning of an atomic system in the mode field maximum. Color\ncenter in diamond, and in particular the negatively-charged Silicon-Vacancy\ncenter, emerged as a promising atom-like systems. Large spectral stability and\naccess to long-lived, nuclear spin memories enabled elementary demonstrations\nof quantum network nodes including memory-enhanced quantum communication. In a\nhybrid approach, we deterministically place SiV$^-$-containing nanodiamonds\ninside one hole of a one-dimensional, free-standing, Si$_3$N$_4$-based photonic\ncrystal cavity and coherently couple individual optical transitions to the\ncavity mode. We optimize the light-matter coupling by utilizing two-mode\ncomposition, waveguiding, Purcell-enhancement and cavity resonance tuning. The\nresulting photon flux is increased by more than a factor of 14 as compared to\nfree-space. The corresponding lifetime shortening to below 460 ps puts the\npotential operation bandwidth beyond GHz rates. Our results mark an important\nstep to realize quantum network nodes based on hybrid quantum photonics with\nSiV$^-$- center in nanodiamonds.\n