Robust all-optical single-shot readout of nitrogen-vacancy centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-22 |
| Journal | Nature Communications |
| Authors | Dominik M. Irber, Francesco Poggiali, Fei Kong, Michael Kieschnick, Tobias LĂŒhmann |
| Institutions | Polish Academy of Sciences, Munich Center for Quantum Science and Technology |
| Citations | 74 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Robust All-Optical Single-Shot Readout of NV Centers
Section titled âTechnical Documentation & Analysis: Robust All-Optical Single-Shot Readout of NV CentersâThis document analyzes the requirements and achievements detailed in the research paper âRobust all-optical single-shot readout of nitrogen-vacancy centers in diamondâ and maps them directly to the advanced Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) solutions offered by 6ccvd.com.
Executive Summary
Section titled âExecutive SummaryâThe research demonstrates a highly robust, all-optical method for achieving single-shot projective readout of Nitrogen-Vacancy (NV) qubit states in diamond, overcoming limitations related to low photon collection efficiency.
- Core Achievement: Successful implementation of an all-optical spin readout scheme achieving single-shot fidelity (SNR > 1) even when photon collection is poor (< 10Âł clicks/second).
- Methodology: Combines spin-dependent resonant excitation at cryogenic temperature with Spin-to-Charge Conversion (SCC), mapping fragile electron spin states to stable charge states.
- Fidelity Metrics: Achieved high end-to-end single-shot fidelity of 88.5 ± 0.5% (Deep NV) and 67.1 ± 0.9% (Shallow NV).
- Signal-to-Noise: Demonstrated a single-shot SNR of 1.74 ± 0.06 on deep NV centers, significantly exceeding the threshold of 1.
- Material Requirement: The technique was proven effective on both deep natural NV centers and shallow implanted NV centers (~70 nm deep), emphasizing the need for high-purity, low-strain Single Crystal Diamond (SCD) substrates.
- Application Relevance: This robust technique is essential for scaling NV-based quantum registers and high-sensitivity shallow NV sensing applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, highlighting the performance achieved using high-quality diamond substrates.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| End-to-End Fidelity (Deep NV) | 88.5 ± 0.5 | % | Single-shot readout (1 ms) |
| End-to-End Fidelity (Shallow NV) | 67.1 ± 0.9 | % | Single-shot readout (5 ms) |
| Single-Shot SNR (Deep NV) | 1.74 ± 0.06 | N/A | Corrected for initialization error |
| Shallow NV Center Depth | ~70 | nm | Created via 110 keV CNâ» implantation |
| Required Photon Collection Rate | < 10Âł | clicks/second | Minimum rate for single-shot fidelity |
| Resonant Laser Wavelength | 637 | nm | Spin-selective excitation |
| Ionization Laser Wavelength | 642 | nm | High-power photoionization |
| Initialization Laser Wavelength | 517 | nm | Charge and spin initialization |
| Deep NV Resonant Power (Readout) | 56 | nW | Used for charge state detection |
| Off-Axial Strain (Deep NV) | 1.73 | GHz | Measured via PLE spectrum |
| Off-Axial Strain (Shallow NV) | 12.6 | GHz | Measured via PLE spectrum |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success hinges on precise control over the diamond material properties and the implementation of a complex, multi-stage optical and microwave pulse sequence.
- Substrate Preparation: High-purity diamond substrates were used. Shallow NV centers were created via 110 keV CN⻠implantation, followed by high-temperature annealing (900 °C for 3 hours, then 1200 °C for 2 hours) to activate the NV centers.
- Cryogenic Environment: All measurements were performed in a Helium flow cryostat to achieve the necessary cryogenic temperatures for resonant excitation and line narrowing.
- Optical Setup: A home-built confocal microscope utilized three independently gateable lasers:
- 637 nm (Narrow-band resonant laser)
- 642 nm (Strong red diode ionization laser)
- 517 nm (Green diode initialization laser)
- Magnetic Field Control: A static magnetic field of ~1 mT was applied, slightly misaligned from the NV axis, to lift spin degeneracies.
- Microwave (MW) Control: Two gateable MW sources were used to drive spin transitions for initialization and to constantly mix spin states during charge readout (Trabi time ~1 ”s).
- Readout Sequence (SCC Protocol):
- Charge Initialization: Green laser (517 nm) pulse.
- Spin Initialization: Resonant depletion of the |0) state followed by an MW Ï-pulse to prepare the desired spin state (e.g., |+1)).
- Spin-Dependent Ionization: Simultaneous application of the 637 nm resonant laser (first photon) and the 642 nm ionization laser (second photon) to selectively ionize the NVâ» center based on its spin state.
- Charge Readout: Low-power detection using the 637 nm resonant laser combined with continuous MW drive.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe demonstrated single-shot readout technique requires diamond substrates of the highest quality, particularly those optimized for low-strain and precise surface engineering necessary for shallow NV implantation. 6CCVD is uniquely positioned to supply the foundational materials required to replicate and advance this research.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the narrow optical linewidths and stable qubit operation demonstrated in the paper, researchers require Electronic Grade Single Crystal Diamond (SCD) with exceptional purity and minimal lattice defects.
| 6CCVD Material Recommendation | Specification | Application Context |
|---|---|---|
| Electronic Grade SCD | Nitrogen concentration < 1 ppb; Low Birefringence | Essential for stable NVâ» centers, minimizing spectral diffusion, and achieving sub-GHz optical linewidths. |
| Optical Grade SCD | High transmission across visible/NIR spectrum | Required for efficient delivery of 517 nm, 637 nm, and 642 nm laser pulses used in the SCC protocol. |
| Custom Substrates | Thickness: 0.1 ”m to 500 ”m | Enables precise control over substrate thickness for integration into micro-optical systems or for subsequent shallow implantation processes. |
Customization Potential
Section titled âCustomization PotentialâThe success of shallow NV centers (70 nm deep) depends critically on the surface quality and geometry of the diamond substrate. 6CCVD offers specialized services to meet these stringent requirements:
- Ultra-Low Roughness Polishing: 6CCVD guarantees surface roughness of Ra < 1nm for SCD wafers, which is critical for minimizing surface defects that contribute to spectral diffusion and charge state instability in shallow NV centers.
- Custom Dimensions: We provide plates and wafers up to 125mm in diameter (PCD) and custom sizes for SCD, allowing for integration into complex cryogenic and microwave setups (e.g., mounting in the flow cryostat).
- Metalization Services: While the paper focuses on optical readout, future scalable quantum registers require integrated microwave delivery. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for fabricating on-chip microwave strip lines directly onto the diamond surface, enabling high-fidelity MW control pulses.
- Precision Fabrication: We offer laser cutting and shaping services to produce custom geometries required for advanced micro-optics or specific sample mounting configurations referenced in the experimental setup.
Engineering Support
Section titled âEngineering SupportâThe creation of high-quality NV centers involves complex post-processing steps (implantation and annealing). 6CCVDâs in-house PhD team specializes in material science and defect engineering, providing expert consultation to researchers:
- Material Selection for Qubit Applications: We assist engineers in selecting the optimal SCD grade (purity, orientation, and thickness) to maximize NV yield, minimize strain, and ensure compatibility with subsequent implantation and annealing protocols for NV-based quantum registers and high-sensitivity sensing projects.
- Surface Optimization: Consultation on achieving the necessary surface termination and quality required for stable charge state control in shallow NV centers.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract High-fidelity projective readout of a qubitâs state in a single experimental repetition is a prerequisite for various quantum protocols of sensing and computing. Achieving single-shot readout is challenging for solid-state qubits. For Nitrogen-Vacancy (NV) centers in diamond, it has been realized using nuclear memories or resonant excitation at cryogenic temperature. All of these existing approaches have stringent experimental demands. In particular, they require a high efficiency of photon collection, such as immersion optics or all-diamond micro-optics. For some of the most relevant applications, such as shallow implanted NV centers in a cryogenic environment, these tools are unavailable. Here we demonstrate an all-optical spin readout scheme that achieves single-shot fidelity even if photon collection is poor (delivering less than 10 3 clicks/second). The scheme is based on spin-dependent resonant excitation at cryogenic temperature combined with spin-to-charge conversion, mapping the fragile electron spin states to the stable charge states. We prove this technique to work on shallow implanted NV centers, as they are required for sensing and scalable NV-based quantum registers.