Proposal for the search for new spin interactions at the micrometer scale using diamond quantum sensors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-05-31 |
| Journal | Physical Review Research |
| Authors | P.-H. Chu, Nathaniel Ristoff, JÄnis Ć mits, Nathan Jackson, Young Jin Kim |
| Institutions | University of New Mexico, Los Alamos National Laboratory |
| Citations | 13 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond for Micrometer-Scale Spin Interaction Sensing
Section titled âTechnical Documentation & Analysis: MPCVD Diamond for Micrometer-Scale Spin Interaction SensingâThis document analyzes the requirements set forth in the research proposal âProposal for the search for new spin interactions at the micrometer scale using diamond quantum sensorsâ (arXiv:2112.14882v1) and maps them directly to 6CCVDâs advanced MPCVD diamond capabilities, positioning 6CCVD as the essential material supplier for replicating and extending this cutting-edge quantum physics research.
Executive Summary
Section titled âExecutive SummaryâThe research proposes using Nitrogen-Vacancy (NV) quantum sensors in diamond to probe exotic spin interactions (V12+13, V4+5, V6+7, V14, V15) at the micrometer scale, projecting sensitivity improvements of up to five orders of magnitude.
- Core Platform: The experiment relies on high-purity, low-strain MPCVD Single Crystal Diamond (SCD) chips containing near-surface NV ensembles.
- Dimensional Precision: Successful replication requires ultra-precise control over diamond layer thickness (down to 0.625 ”m) and minimal NV-test mass standoff (as low as 0.2 ”m), necessitating Ra < 1 nm polishing.
- Advanced Material Requirement: Probing velocity-dependent spin-spin interactions (V6+7, V14, V15) demands a spin-polarized test mass, specifically a thin membrane of hyperpolarized 13C enriched diamond.
- Custom Orientation: Optimal spin polarization transfer (PulsePol) and interaction maximization require specific crystal orientations, such as (110) for the sensor and (111) for the test mass.
- Integration Support: The MEMS oscillator design requires custom metalization (e.g., Au, Ti) for electrode pads, a capability offered in-house by 6CCVD.
- 6CCVD Value Proposition: 6CCVD is uniquely positioned to supply the required custom SCD and isotopically enriched diamond substrates with the necessary thickness control, orientation, and surface finish to meet these stringent quantum sensing requirements.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the critical material and operational parameters required by the proposed experimental geometries (Tables I and II in the paper).
| Parameter | Value Range | Unit | Context / Requirement |
|---|---|---|---|
| Target Interaction Length (λ) | 0.5, 5, 50 | ”m | Optimization targets for unpolarized test masses |
| NV Layer Thickness (dnv) | 0.625 to 62.5 | ”m | Optimized as 1.25 * λ; requires precise thin film SCD |
| Minimum Gap (dgap) | 0.2 to 5 | ”m | NV-test mass standoff; requires ultra-flat surfaces |
| Test Mass Radius (Rtm) | 150 | ”m | Standardized radius for all geometries |
| Polarized Test Mass Thickness (dtm) | 2 | ”m | Thin membrane required to minimize stray magnetic fields |
| Modulation Frequency (fm) | 1 | MHz | Required for high peak velocity |
| Peak Test Mass Velocity (v) | 4.7 | m/s | Achieved via MEMS oscillator actuation |
| Estimated Magnetic Sensitivity (Bmin) | 6 to 10 | pT | Required sensitivity for t = 1 s averaging |
| Required 13C Spin Density (Ï) | 5 x 1025 | m-3 | Hyperpolarized 13C diamond test mass |
| Sensor Crystal Orientation | (110) | Surface | Required for NV axis in-plane alignment |
| Test Mass Crystal Orientation | (111) | Surface | Required for 13C axis normal alignment |
Key Methodologies
Section titled âKey MethodologiesâThe proposed experiments rely on highly specialized material preparation and quantum control techniques:
- Diamond Substrate Engineering: Utilization of MPCVD diamond chips with precise, near-surface NV layers (dnv < 1 ”m for the smallest λ target) to maximize coupling to the micrometer-scale test mass.
- Hyperpolarization Technique: Implementation of the PulsePol protocol to achieve high nuclear spin polarization (Ï â 5 x 1025 m-3) in a thin 13C enriched diamond membrane test mass.
- MEMS Integration: Attachment of the diamond sensor and test mass (SiO2 or 13C diamond) to a high-frequency (1 MHz) electrostatic comb-drive MEMS oscillator to generate high peak velocity (4.7 m/s) lateral motion.
- Phase-Sensitive Detection: Use of the XY8-N multi-pulse quantum sensing protocol, which acts as a phase-sensitive bandpass filter centered at the mechanical oscillation frequency (fm), effectively suppressing low-frequency noise and systematic drifts.
- Systematic Error Mitigation: Strategies including performing the experiment under vacuum, alternating NV spin transitions, and exploiting the 90° phase difference between displacement (stray magnetic fields) and velocity (exotic interaction fields) to isolate the desired signal.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the foundational MPCVD diamond materials and customization services necessary to execute this demanding research, ensuring optimal performance and systematic error mitigation.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Material Solution | Specification Match |
|---|---|---|
| NV Sensor Layer (dnv) | Optical Grade SCD | SCD thickness control from 0.1 ”m to 500 ”m, perfectly matching the required dnv range (0.625 ”m to 62.5 ”m). |
| Polarized Test Mass | Isotopically Enriched Diamond | Custom 13C enriched diamond substrates (up to 10 mm thick) for hyperpolarization, enabling the high spin density (5 x 1025 m-3) required for V6+7, V14, and V15. |
| Large Area Test Mass | Optical Grade PCD | For large-area test mass geometries (Rtm = 150 ”m), 6CCVD offers PCD wafers up to 125 mm in diameter, ensuring material uniformity. |
| MEMS Integration | BDD (Boron-Doped Diamond) | BDD substrates can be supplied for specific electrical or thermal management requirements within the MEMS structure. |
Customization Potential
Section titled âCustomization PotentialâThe success of this proposal hinges on precise material geometry and integration capabilities, which are core strengths of 6CCVD:
- Ultra-Thin Film Control: The requirement for dnv down to 0.625 ”m and dtm of 2 ”m is met by 6CCVDâs advanced MPCVD growth and etching capabilities, providing films as thin as 0.1 ”m.
- Precision Polishing: Achieving the critical sub-micrometer gap (dgap < 0.5 ”m) between the sensor and test mass necessitates exceptional surface quality. 6CCVD guarantees Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, minimizing systematic errors from surface charges and air friction.
- Custom Crystal Orientation: 6CCVD supplies SCD substrates with specific surface polishes, enabling the required (110) sensor and (111) test mass orientations critical for maximizing the interaction signal and optimizing the PulsePol sequence (Fig. 10c).
- In-House Metalization: The MEMS oscillator design (Fig. 12) requires metal pads for actuation. 6CCVD offers internal metalization services, including Ti, Au, Pt, Pd, W, and Cu, allowing for seamless integration of the diamond chip into the micro-mechanical device.
Engineering Support
Section titled âEngineering SupportâThe complexity of mitigating systematic errorsâsuch as those arising from stray magnetic fields (Section VII.F) and surface charges (Section VII.C)ârequires expert material knowledge.
- PhD-Level Consultation: 6CCVDâs in-house PhD team specializes in MPCVD diamond for quantum sensing applications. We offer consultation on material selection, doping profiles, and crystal orientation to optimize the NV ensemble properties (density, coherence time T2*) for similar Spin-Velocity Interaction projects.
- Global Supply Chain: 6CCVD ensures reliable, global shipping (DDU default, DDP available) of sensitive, custom diamond materials, supporting international research collaborations.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
For decades, searches for exotic spin interactions have used increasingly precise laboratory measurements to test various theoretical models of particle physics. However, most searches have focused on interaction length scales of âł 1 mm, corresponding to hypothetical boson masses of âČ 0.2 meV. Recently, quantum sensors based on nitrogen-vacancy (NV) centers in diamond have emerged as a promising platform to probe spin interactions at the micrometer scale, opening the door to explore new physics at this length scale. Here, we propose experiments to search for several hypothetical interactions between NV electron spins and moving masses. We focus on potential interactions involving the coupling of NV spin ensembles to both spin-polarized and unpolarized masses attached to vibrating mechanical oscillators. For each interaction, we estimate the sensitivity, identify optimal experimental conditions, and analyze potential systematic errors. Using multipulse quantum sensing protocols with NV spin ensembles to improve sensitivity, we project constraints that are a 5-orders-of-magnitude improvement over previous constraints at the micrometer scale. We also identify a spin-polarized test mass, based on hyperpolarized <sup>13</sup>C nuclear spins in a thin diamond membrane, which offers a favorable combination of high spin density and low stray magnetic fields. Our analysis is timely in light of a recent preprint by Rong et al. (arXiv:2010.15667) reporting a surprising nonzero result of micrometer-scale spin-velocity interactions.