Selective noise resistant gate
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-12-07 |
| Journal | Physical review. B./Physical review. B |
| Authors | Jonatan Zimmermann, Paz London, Yaniv Yirmiyahu, Fedor Jelezko, Aharon Blank |
| Institutions | UniversitĂ€t Ulm, Technion â Israel Institute of Technology |
| Citations | 4 |
| Analysis | Full AI Review Included |
Technical Analysis: Selective Noise Resistant Gate using MPCVD Diamond
Section titled âTechnical Analysis: Selective Noise Resistant Gate using MPCVD DiamondâThis document analyzes the research detailing the Selective Noise Resistant Gate (SNRG) protocol implemented on a single Nitrogen-Vacancy (NV) center in diamond. The findings demonstrate a critical advancement in solid-state quantum registers by simultaneously achieving high gate fidelity and narrow spectral bandwidth (selectivity), directly addressing the trade-off inherent in closely spaced qubit systems.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Successful experimental demonstration of the Selective Noise Resistant Gate (SNRG) protocol using a single NV center in diamond.
- Performance Metrics: Achieved high quantum gate fidelity (F = 0.9 ± 0.02) and high selectivity, quantified by a narrow spectral bandwidth (BW = 49 ± 5 kHz).
- Methodology: The SNRG scheme combines noise protection via Dynamical Decoupling (DD) sequences with magnetic gradient-based selectivity, crucially employing alternating positive and negative magnetic field gradients synchronized with DD pulses.
- Material Requirement: The experiment relies on high-purity, low-nitrogen diamond (Type IIa) to ensure long spin coherence times (T2* ~ 5 ”s), essential for robust quantum operations.
- Scalability: The protocol enables selective control of individual qubits in interacting arrays, requiring relatively moderate magnetic gradients (~1 mG/nm) compared to previous methods.
- 6CCVD Value Proposition: 6CCVD provides the necessary high-purity Single Crystal Diamond (SCD) substrates, custom dimensions, and integrated metalization capabilities required to replicate and scale this advanced quantum architecture.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters were extracted from the experimental results and modeling of the NV center system:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Gate Fidelity (F) | 0.9 ± 0.02 | Dimensionless | Achieved using the SNRG protocol |
| Spectral Bandwidth (BW) | 49 ± 5 | kHz | SNRG selectivity performance (almost 10x narrower than unprotected) |
| Rabi Frequency (Ω) | 54 | kHz | Continuous driving frequency for on-resonance spin |
| Dephasing Time (T2*) | 5 ± 1 | ”s | Measured coherence time of the NV center |
| Effective Noise Coupling (b) | 42 | kHz | Fitted parameter for 13C nuclear spin bath noise |
| Bath Correlation Time (Ïc) | 230 | ”s | Fitted parameter for Ornstein-Uhlenbeck process |
| Required Future Gradient | 1 | mG/nm | Estimated gradient needed for 10 nm proximate spin separation |
| Longitudinal Field (Bz) Amplitude | 30 - 100 | mG | Scanned range for performance investigation |
| NV Center Distance from Microwire | 20 | ”m | Used for magnetic gradient calibration |
Key Methodologies
Section titled âKey MethodologiesâThe SNRG protocol is a complex sequence integrating optical, microwave, and magnetic field control, designed to overcome the limitations of standard Rabi and Dynamically Protected Gates (DPG).
- Material System: Utilized the electronic spin of a single Nitrogen-Vacancy (NV) center in high-purity diamond (Type IIa).
- Initialization and Readout: Spin state initialized and read out using a 532 nm laser.
- Microwave Driving: Applied via crossing microwires stretched on the diamond surface, utilizing Frequency Modulation (FM) to follow instantaneous changes in the magnetic field.
- Magnetic Field Control: The longitudinal magnetic field (Bz) was applied by an external permanent magnet (B0) combined with a pulsed field (B1) generated by a proximate microwire.
- SNRG Sequence Implementation: The gate sequence consists of laser initialization, readout, pulsed magnetic field gradient, and a modified XY-8 Dynamical Decoupling (DD) sequence.
- Gradient Alternation (Key Innovation): The magnetic gradient (detuning Îz) was alternated between positive and negative values after each DD Ï pulse. This critical step ensures that the detuning term accumulates constructively (maintaining selectivity) while the noise effects are canceled out (maintaining fidelity).
- Phase Cycling: Microwave driving phase was inverted after each uncommutable DD operator (e.g., ÏY) to ensure constructive accumulation of the desired control gate rotation.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful implementation and future scaling of the SNRG protocol depend critically on the quality and customization of the diamond substrate and integrated components. 6CCVD is uniquely positioned to supply the necessary materials and engineering services.
Applicable Materials for Quantum Registers
Section titled âApplicable Materials for Quantum RegistersâTo replicate or extend this research, particularly toward high-density NV arrays, the highest quality diamond is mandatory to maximize T2 and T2* coherence times.
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Optical Grade Single Crystal Diamond (SCD):
- Requirement Match: The paper uses an NV center in diamond, requiring extremely low intrinsic nitrogen concentration (Type IIa) to minimize decoherence from the 13C nuclear spin bath and residual nitrogen impurities.
- 6CCVD Solution: We supply high-purity SCD wafers (0.1 ”m to 500 ”m thickness) with guaranteed low defect density, ideal for creating long-lived qubits and supporting advanced quantum protocols like SNRG.
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Boron-Doped Diamond (BDD) (For Sensing/Electrochemistry Extension):
- Extension Potential: While the paper focuses on NV qubits, the ability to control spin dynamics under high magnetic gradients is also crucial for diamond-based magnetometers and electrochemistry.
- 6CCVD Solution: We offer custom Boron-Doped Diamond (BDD) films for applications requiring conductive diamond electrodes or specialized quantum sensing platforms.
Customization Potential for Integrated Devices
Section titled âCustomization Potential for Integrated DevicesâThe experimental setup relies on precise microwire placement and field generation, necessitating highly controlled substrate geometry and surface preparation.
| Requirement from Paper | 6CCVD Customization Capability | Technical Advantage |
|---|---|---|
| Microwire Integration | Custom Metalization Services | We offer in-house deposition of standard stacks (Ti/Pt/Au, Ti/W/Cu) directly onto the diamond surface, enabling robust, low-resistance microwave circuitry for driving fields. |
| Substrate Dimensions | Custom Plates/Wafers | We provide SCD and PCD plates up to 125 mm in diameter, allowing researchers to scale up from single-qubit experiments to multi-qubit arrays. |
| Surface Quality | Ultra-Low Roughness Polishing | Our SCD polishing achieves Ra < 1 nm, ensuring optimal surface flatness for high-resolution lithography and reliable adhesion of the integrated microwires used to generate the magnetic gradient. |
| Thickness Control | SCD/PCD Thickness Control | We offer precise thickness control from 0.1 ”m to 500 ”m (SCD/PCD) and substrates up to 10 mm, critical for optimizing optical access and thermal management in complex setups. |
Engineering Support
Section titled âEngineering SupportâThe paper highlights the challenge of achieving the required future magnetic gradient of 1 mG/nm and the sensitivity to experimental imperfections (e.g., AWG jitter). 6CCVDâs in-house PhD team provides expert consultation to mitigate material-related limitations.
- Material Optimization: We assist researchers in selecting the optimal diamond growth parameters (e.g., nitrogen concentration, isotopic purity) to maximize T2 coherence times for similar NV-based Quantum Register projects.
- Surface Engineering: We provide guidance on surface termination and preparation techniques necessary for high-fidelity lithography and subsequent metalization required for integrated microwave and gradient structures.
- Global Logistics: We ensure reliable global shipping (DDU default, DDP available) for sensitive, high-value diamond materials, supporting international research collaborations.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Realizing individual control on single qubits in a spin-based quantum\nregister is an ever-increasing challenge due to the close proximity of the\nqubits resonance frequencies. Current schemes typically suffer from an inherent\ntrade-off between fidelity and qubits selectivity. Here, we report on a new\nscheme which combines noise protection by dynamical decoupling and magnetic\ngradient based selectivity, to enhance both the fidelity and the selectivity.\nWith a single nitrogen-vacancy center in diamond, we experimentally demonstrate\nquantum gates with fidelity = 0.9 $\pm$ 0.02 and a 50 kHz spectral bandwidth,\nwhich is almost an order of magnitude narrower than the unprotected bandwidth.\nOur scheme will enable selective control of an individual nitrogen-vacancy\nqubit in an interacting qubits array using relatively moderate gradients of\nabout 1 mG/nm.\n