Environmentally Mediated Coherent Control of a Spin Qubit in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-04-19 |
| Journal | Physical Review Letters |
| Authors | Scott E. Lillie, David A. Broadway, James D. A. Wood, David Simpson, Alastair Stacey |
| Institutions | Centre for Quantum Computation and Communication Technology, Melbourne Centre for Nanofabrication |
| Citations | 15 |
| Analysis | Full AI Review Included |
Environmentally Mediated Resonance (EMR) in Diamond Qubits: A 6CCVD Technical Analysis
Section titled âEnvironmentally Mediated Resonance (EMR) in Diamond Qubits: A 6CCVD Technical AnalysisâResearch Paper: Lillie et al., Environmentally mediated coherent control of a spin qubit in diamond (arXiv:1702.05822v1, 2017)
This analysis translates the core findings of advanced quantum control research into high-density technical specifications and connects them directly to 6CCVDâs MPCVD diamond fabrication capabilities, focusing on materials necessary to replicate or advance this quantum technology.
Executive Summary
Section titled âExecutive SummaryâThe research details a novel technique, Environmentally Mediated Resonance (EMR), utilizing proximal environmental electron spins in diamond to achieve coherent control of single Nitrogen-Vacancy (NV) spin qubits.
- Core Achievement: Demonstration of EMR-driven coherent control of single NV centers, including Rabi oscillations, free induction decay (Ramsey), and spin-echo measurements.
- Mechanism: Control is achieved by matching the Rabi frequency of driven environmental spins (surface free electrons or P1 centers) with the NV qubit transition frequency ($\Omega_{\text{env}} = \omega_{\text{NV}}$).
- Material Requirement: Requires ultra-pure, electronic-grade Single Crystal Diamond (SCD) grown via CVD to ensure high crystal quality and long qubit coherence times ($T_2$).
- NV Implementation: Qubits are shallow 15NV centers (5-15 nm deep), formed via low-energy ion implantation into a [100]-oriented substrate, demanding pristine surface quality.
- Application Potential: EMR simplifies nanoscale Electron Spin Resonance (ESR) spectroscopy, enabling the selective addressing and mapping of environmental spin distribution, critical for quantum sensing and scalable quantum architectures.
- 6CCVD Relevance: Successful replication and scaling of this work requires high-pcoherence SCD substrates and precision fabrication techniques (polishing, metalization, and controlled doping) offered by 6CCVD.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard parameters define the material properties and experimental conditions required for successful EMR operation of the NV qubit.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Crystal Grade | Electronic Grade CVD | N/A | Essential for low strain and high NV coherence ($T_{2}$ â 3 ”s). |
| Diamond Orientation | [100] | N/A | Substrate orientation for growth/implantation. |
| NV Species & Depth | 15NV | N/A | Formed 5-15 nm below the surface via 3.5 keV ion implantation. |
| Implantation Fluence | 109 | cm-2 | Low density, single-NV creation. |
| Annealing Temperature | 800 | °C | Required under UHV for 5 hours to activate NVs. |
| Static Magnetic Field ($B_{0}$) | 1023 - 1024.8 | G | External field tuned near the Ground-State Level Anti-Crossing (GSLAC). |
| Environmental Spin Freq ($\omega_{\text{env}}$) | 2860 - 2880 | MHz | Free-electron spins on surface/bulk defects (e.g., P1). |
| Optimal NV Transition Freq ($\omega_{\text{NV}}$) | 2.65 | MHz | Transition frequency chosen for EMR matching. |
| Achieved NV Rabi Frequency ($\Omega_{\text{NV}}$) | 3.3 | MHz | Coherent control speed demonstrated via EMR. |
| Shortest Pulse Duration ($\pi/2$) | 650 | ns | Time required for NV spin flip during EMR Rabi. |
| Spectral Resolution (P1 Center FWHM) | 5 | MHz | Resolution achieved using EMR spectroscopy. |
Key Methodologies
Section titled âKey MethodologiesâThe core EMR experiment relies on precise material engineering and pulsed microwave/optical control within a high DC magnetic field environment.
- Diamond Synthesis: Utilization of [100]-oriented, Electronic Grade Single Crystal Diamond (SCD) grown via Microwave Plasma Chemical Vapor Deposition (MPCVD).
- Shallow Defect Formation: Creation of single NV centers (qubits) by ultra-low energy ion implantation (3.5 keV) of 15N into the SCD surface, resulting in an estimated 5-15 nm depth.
- Post-Processing Annealing: High-temperature annealing (800 °C, 5 hours, UHV) is necessary to mobilize vacancies and form stable NV centers.
- Field Alignment: An external magnetic field ($B_{0}$) is applied parallel to the NV quantization axis, precisely tuned to approximately 1024 G to reach the GSLAC regime, minimizing $\omega_{\text{NV}}$ to facilitate the EMR matching condition.
- EMR Drive Sequence: Environmental spins are directly driven by a global microwave field ($\omega_{\text{MW}}$) at frequencies near $\omega_{\text{env}}$ (2860-2880 MHz).
- Qubit Control: Coherent control is achieved when the environmental spin Rabi frequency ($\Omega_{\text{env}}$) is tuned to match the NV transition frequency ($\omega_{\text{NV}}$), allowing the environmental spins to act as localized control agents.
- Optical Readout: Single NV spin state readout is performed using standard confocal microscopy techniques involving 532 nm laser excitation and Photoluminescence (PL) collection.
6CCVD Solutions & Capabilities: Enabling Advanced EMR Qubit Research
Section titled â6CCVD Solutions & Capabilities: Enabling Advanced EMR Qubit Researchâ6CCVD is uniquely positioned to supply the foundational SCD materials and advanced fabrication services required to replicate and scale this cutting-edge EMR technology for quantum computing and sensing applications.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the long coherence times and high crystal quality necessary for successful EMR experiments, the following 6CCVD materials are required:
- Optical Grade Single Crystal Diamond (SCD): This material ensures the lowest possible concentration of native point defects (< 1 ppb N), minimizing intrinsic decoherence sources and providing an ideal host for engineered shallow NVs.
- Controlled Nitrogen Doping SCD (P1 Centers): For experiments extending the EMR concept to control specific bulk environmental spins (P1 centers, as demonstrated in Fig. 5), 6CCVD can supply SCD wafers with precise, controlled nitrogen doping concentrations established during the MPCVD growth process.
Customization Potential for EMR Systems
Section titled âCustomization Potential for EMR SystemsâThe complexity of EMR requires integration of microwave components (micro-wires) and precision surface engineering. 6CCVD offers end-to-end customization services:
| Fabrication Requirement | 6CCVD Service Offering | Technical Necessity in EMR Context |
|---|---|---|
| Pristine Surfaces | Ultra-Low Roughness Polishing (Ra < 1 nm SCD) | Critical for shallow NV implantation (5-15 nm depth) and minimizing surface-induced decoherence from free electron spins. |
| Microwave Circuitry | Custom Metalization (Ti, Pt, Au, Cu) | Deposition of thin-film metal stacks required for fabricating micro-wires and planar waveguides to generate the high-frequency microwave fields ($B_{1}$) driving the environmental spins. |
| Qubit Integration | Precision Dimensions & Laser Cutting | Custom plates/wafers (up to 125 mm PCD) cut, diced, and micro-machined to integrate into specific quantum cryostat or confocal microscope architectures. |
| Material Thickness | Customizable SCD Thickness (0.1 ”m - 500 ”m) | Flexibility in providing ultra-thin films for advanced integration or thick substrates (up to 10 mm) for structural rigidity and heat dissipation. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and technical engineers provides authoritative support on complex quantum projects. We assist clients with:
- Material Selection: Determining the optimal balance between high $T_{2}$ (low native nitrogen) and controlled environmental spin density (P1 centers) for specific NV-EMR Quantum Sensing and Spectroscopy applications.
- Surface Preparation: Guidance on the optimal surface termination and polishing protocols for successful ultra-shallow ion implantation and subsequent UHV annealing procedures.
- Metal Stack Optimization: Consulting on metalization layer adhesion, resistivity, and patterning for developing efficient on-chip microwave delivery systems.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The coherent control of spin qubits forms the basis of many applications in quantum information processing and nanoscale sensing, imaging, and spectroscopy. Such control is conventionally achieved by direct driving of the qubit transition with a resonant global field, typically at microwave frequencies. Here we introduce an approach that relies on the resonant driving of nearby environment spins, whose localized magnetic field in turn drives the qubit when the environmental spin Rabi frequency matches the qubit resonance. This concept of environmentally mediated resonance (EMR) is explored experimentally using a qubit based on a single nitrogen-vacancy (NV) center in diamond, with nearby electronic spins serving as the environmental mediators. We demonstrate EMR driven coherent control of the NV spin state, including the observation of Rabi oscillations, free induction decay, and spin echo. This technique also provides a way to probe the nanoscale environment of spin qubits, which we illustrate by acquisition of electron spin resonance spectra from single NV centers in various settings.