Experimental Constraint on an Exotic Parity-Odd Spin- and Velocity-Dependent Interaction with a Single Electron Spin Quantum Sensor

At a Glance

Metadata	Details
Publication Date	2021-06-29
Journal	Physical Review Letters
Authors	Man Jiao, Maosen Guo, Xing Rong, Yi-Fu Cai, Jiangfeng Du
Institutions	Hefei National Center for Physical Sciences at Nanoscale, CAS Key Laboratory of Urban Pollutant Conversion
Citations	33
Analysis	Full AI Review Included

Technical Documentation & Analysis: Exotic Spin-Dependent Interaction Sensing via NV Diamond

This document analyzes the research paper “Experimental Constraint on an Exotic Parity-Odd Spin- and Velocity-Dependent Interaction with a Single Electron Spin Quantum Sensor” (arXiv:2009.09257v1) to highlight the critical role of high-quality MPCVD diamond and to propose specific material solutions offered by 6CCVD.

Executive Summary

The research successfully utilized a single Nitrogen-Vacancy (NV) center in diamond as a quantum sensor to establish new constraints on exotic physics interactions beyond the Standard Model.

Core Achievement: Established an improved laboratory upper bound on the exotic parity-odd spin- and velocity-dependent interaction between an electron spin and unpolarized nucleons.
Sensor Platform: A near-surface NV center (< 10 nm depth) in Single Crystal Diamond (SCD) was used as the highly sensitive electron spin quantum sensor.
Methodology: The experiment measured the effective magnetic field generated by a vibrating fused silica half-sphere (nucleon source) using synchronized microwave and laser pulses (quantum control).
Key Result: The upper limit of the coupling $g_A g_V^N$ was constrained to $\le 8.0 \times 10^{-19}$ at a force range ($\lambda$) of 200 µm.
Impact: This result significantly improves the current laboratory limit within the 1 to 330 µm force range by more than four orders of magnitude.
Future Improvement: The paper explicitly notes that sensitivity is currently limited by the coherence time ($T_2$) of the NV center, requiring higher purity diamond substrates for future work.

Technical Specifications

The following hard data points were extracted from the experimental setup and results:

Parameter	Value	Unit	Context
Substrate Orientation	<100>	N/A	Bulk diamond used for NV creation
NV Center Depth	< 10	nm	Required for near-surface sensing
N⁺ Implantation Energy	10	keV	Used to create NV centers
Annealing Temperature	800	°C	Post-implantation defect activation
Oxidative Etching Temperature	580	°C	Surface preparation
Static Magnetic Field (B₀)	565	Gauss	Applied along NV axis to lift degeneracy
Source Diameter (M)	500	µm	Fused silica half-sphere
Minimal Distance (d₀)	2.0 ± 0.1	µm	Distance between NV and source
Vibration Amplitude (A)	165.2 ± 0.1	nm	Source movement amplitude
*Dephasing Time (T₂)**	27 ± 4	µs	Electron spin coherence time (Spin Echo)
Force Range Tested ($\lambda$)	1 to 330	µm	Range where improved bounds were set
Upper Limit on Coupling ($g_A g_V^N$)	$\le 8.0 \times 10^{-19}$	N/A	Established at $\lambda = 200$ µm (95% CL)
Total Systematic Error Correction	(1.0 ± 5.4) $\times 10^{-20}$	N/A	Correction to $g_A g_V^N$

Key Methodologies

The experiment relied on precise material engineering and advanced quantum control techniques:

Substrate Selection and Preparation: Use of bulk <100> diamond. NV centers were created via 10 keV N⁺ ion implantation, followed by 2 hours of annealing at 800 °C.
Surface Engineering: The diamond surface underwent 4 hours of oxidative etching at 580 °C. Nanopillars were fabricated to enhance the photoluminescence (PL) detection efficiency, achieving 350 kcounts/s.
Setup Integration: The NV sensor was integrated with an Atomic Force Microscope (AFM) tuning fork actuator, which provided the vibrating mass source (fused silica half-sphere, 500 µm diameter).
Magnetic Field Control: A 565 Gauss static magnetic field ($B_0$) was applied along the NV symmetry axis to remove the degeneracy of the $|m_s = \pm 1\rangle$ spin states.
Quantum State Manipulation: Microwave pulses, delivered via a copper wire placed on the diamond surface, were synchronized with the source vibration to perform spin initialization ($\pi/2$ pulses), inversion ($\pi$ pulses), and readout (via green laser pulses).
Phase Accumulation: Dynamical decoupling techniques were employed to suppress unwanted magnetic noise, allowing the NV spin to accumulate a phase factor ($\Phi$) dependent only on the exotic effective magnetic field ($B_{eff}$) arising from the moving nucleons.

6CCVD Solutions & Capabilities

The success and future scalability of this research hinge on the quality and customization of the diamond substrate. 6CCVD provides the necessary high-purity materials and engineering services required to replicate and significantly extend these quantum sensing experiments.

Applicable Materials

To achieve the long coherence times ($T_2$) necessary to improve the sensitivity (as noted by the authors), researchers require the highest quality Single Crystal Diamond (SCD).

Application Requirement	6CCVD Material Recommendation	Technical Specification
Quantum Sensor Substrate	Optical Grade Single Crystal Diamond (SCD)	Ultra-low nitrogen content (< 1 ppb) to maximize $T_2$ coherence time, essential for enhanced sensitivity.
Orientation Control	SCD Wafers in <100> or <111> orientation	Provides the necessary crystallographic alignment for precise NV axis definition and implantation.
Alternative Sensing	Boron-Doped Diamond (BDD)	For related experiments requiring electrochemical sensing or high-sensitivity magnetometry using alternative defects.

Customization Potential

6CCVD’s in-house engineering capabilities directly address the complex fabrication and integration challenges presented in this research:

Paper Requirement/Future Need	6CCVD Customization Service	Benefit to Researcher
Precise Dimensions & Thickness	Custom plates/wafers up to 125mm in size. SCD thickness from 0.1 µm to 500 µm.	Allows for optimization of the sensor geometry and integration into specialized AFM/vacuum systems.
Surface Microwave Delivery	Custom Metalization: Internal capability for depositing Au, Pt, Pd, Ti, W, and Cu films.	We can deposit the required copper (Cu) microwave striplines directly onto the diamond surface with high precision, ensuring optimal quantum control fidelity.
Ultra-Low Roughness	Polishing Services: Ra < 1 nm for SCD.	Critical for minimizing surface defects that degrade near-surface NV coherence and for high-fidelity nanopillar/etching fabrication.
Integration Geometry	Laser Cutting and Shaping: Custom shaping and dicing of substrates.	Enables the creation of complex geometries needed for close proximity sensing (e.g., mounting on tuning forks or specialized cantilevers).

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth parameters optimized for quantum applications. We offer consultation on:

Material Selection: Choosing the optimal SCD grade and orientation to maximize NV center $T_2$ and $T_1$ times.
Surface Preparation: Advising on pre- and post-processing steps (e.g., etching, termination) to maintain high-quality near-surface NV centers.
Integration: Providing substrates with custom metalization patterns ready for immediate integration into similar NV-based Quantum Sensing projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures rapid delivery of specialized diamond materials worldwide.

View Original Abstract

Improved laboratory limits on the exotic spin- and velocity-dependent interaction at the micrometer scale are established with a single electron spin quantum sensor. The single electron spin of a near-surface nitrogen-vacancy center in diamond is used as the quantum sensor, and a fused-silica half-sphere lens is taken as the source of the moving nucleons. The exotic interaction between the polarized electron and the moving nucleon source is explored by measuring the possible magnetic field sensed by the electron spin quantum sensor. Our experiment sets improved constraints on the exotic spin- and velocity-dependent interaction within the force range from 1.4 to 330 μm. The upper limit of the coupling g_{A}^{e}g_{V}^{N} at 200 μm is |g_{A}^{e}g_{V}^{N}|≤5.3×10^{-19}, significantly improving the current laboratory limit by more than 4 orders of magnitude.

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevlett.127.010501