Experimental Constraint on an Exotic Parity-Odd Spin- and Velocity-Dependent Interaction with a Single Electron Spin Quantum Sensor
At a Glance
Section titled “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 | CAS Key Laboratory of Urban Pollutant Conversion, University of Science and Technology of China |
| Citations | 33 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research establishes a significantly improved laboratory constraint on an exotic parity-odd spin- and velocity-dependent interaction, potentially mediated by axion-like particles, using a quantum sensing platform.
- Core Achievement: Established the most stringent laboratory upper bound on the exotic coupling constant gAgV in the micrometer force range (1 to 330 µm).
- Sensitivity Improvement: The constraint on |gAgV| at 200 µm (less than or equal to 8.0 x 10-19) improves upon previous laboratory limits by more than four orders of magnitude.
- Quantum Sensor: A single electron spin of a near-surface Nitrogen-Vacancy (NV) center in diamond was utilized as the highly sensitive quantum magnetometer.
- Source Mechanism: The source of moving nucleons was a fused silica half-sphere lens mounted on an Atomic Force Microscope (AFM) tuning fork, providing a controlled, vibrating mass source.
- Detection Principle: The experiment measured the accumulated phase factor on the NV spin state, synchronized with the velocity of the moving mass, which would arise from the effective magnetic field (Beff) generated by the exotic interaction.
- Methodology: Delicate quantum control techniques, including dynamical decoupling (spin echo), were employed to suppress magnetic noise and enhance sensor coherence time (T2 = 27 µs).
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sensor Type | Single Electron Spin | N/A | Near-surface NV center in diamond. |
| NV Center Depth | Less than 10 | nm | Proximity to the diamond surface. |
| NV Creation Method | 10 keV N+ ion implantation | N/A | Followed by high-temperature annealing. |
| Annealing Temperature | 800 | °C | Used for NV center activation. |
| Oxidative Etching Temperature | 580 | °C | Applied for 4 hours post-annealing. |
| Source Material | Fused Silica | N/A | Half-sphere lens (nucleon source). |
| Source Diameter | 500 | µm | Diameter of the half-sphere lens. |
| Minimal Distance (d0) | 2.0 ± 0.1 | µm | Distance between NV center and source bottom. |
| External Magnetic Field (B0) | 565 | Gauss | Applied along the NV symmetry axis to lift spin degeneracy. |
| Spin Dephasing Time (T2) | 27 ± 4 | µs | Measured using the spin echo technique. |
| Vibration Amplitude (A) | 165.2 ± 0.1 | nm | Amplitude of the mass source vibration. |
| Vibration Frequency (ωM/2π) | 74.452 | kHz | Frequency of the AFM tuning fork actuator. |
| Phase Accumulation Time (τ) | 6.652 | µs | Waiting time duration for spin evolution. |
| Improved Force Range | 1 to 330 | µm | Range where the new experimental bound is set. |
| Upper Limit (gAgV) at 200 µm | Less than or equal to 8.0 x 10-19 | N/A | Achieved 95% confidence level constraint. |
| Total Systematic Error Correction | (1.0 ± 5.4) x 10-20 | N/A | Correction applied to the gAgV coupling constant. |
Key Methodologies
Section titled “Key Methodologies”- NV Center Fabrication: NV centers were created in bulk diamond via 10 keV N+ ion implantation, followed by annealing at 800 °C. The diamond surface was subsequently oxidized at 580 °C and fabricated into nanopillars to enhance photoluminescence collection efficiency (350 kcounts/s).
- Spin State Preparation and Readout: A pulsed green laser (200 µW power) was used to initialize the NV electron spin state to |ms = 0> and for subsequent photoluminescence readout.
- Quantum State Encoding: The spin states |ms = 0> and |ms = -1> were encoded as the quantum sensor, sensitive to magnetic fields, with microwave pulses delivered via a copper wire on the diamond surface.
- Moving Nucleon Source: A 500 µm diameter fused silica half-sphere lens was mounted on an AFM tuning fork actuator, providing a controlled vibration (A = 165.2 nm, 74.452 kHz) to generate the relative velocity (v) required for the exotic interaction.
- Synchronized Pulse Sequence: The microwave pulse sequence (π/2, π, π/2 pulses) was synchronized with the vibration cycle of the mass source using a pulse generator and comparator.
- Phase Accumulation Measurement: A spin echo sequence was used to accumulate a phase factor (φ) proportional to the integral of the effective magnetic field (Beff) over time. By comparing measurements taken when the π/2 pulses occurred at minimal (P+) versus maximal (P-) source distance, the signal I = P+ - P- was isolated.
- Noise Suppression: Dynamical decoupling techniques were employed to suppress unwanted magnetic noise, maximizing the sensitivity of the NV center to the weak, modulated Beff signal.
Commercial Applications
Section titled “Commercial Applications”The technology and techniques demonstrated in this research are highly relevant to the development of next-generation quantum sensing devices and fundamental physics platforms.
- Nanoscale Quantum Sensing: Utilizing near-surface NV centers for ultra-sensitive detection of weak, localized magnetic fields, applicable in material science and biological imaging.
- Fundamental Physics Platforms: Establishing NV centers as a robust, scalable platform for searching for physics beyond the Standard Model (BSM), including testing exotic spin-dependent forces and dark matter candidates.
- High-Precision Magnetometry: Development of compact, solid-state magnetometers capable of operating at room temperature with high spatial resolution and sensitivity, suitable for industrial quality control and electronics testing.
- Inertial Sensing and Gravimetry: The demonstrated sensitivity to velocity-dependent interactions provides a pathway for developing highly sensitive inertial sensors or accelerometers based on quantum spin manipulation.
- Advanced Diamond Materials: The requirement for high-quality, near-surface NV centers drives innovation in diamond growth (CVD) and surface engineering techniques necessary for creating robust quantum devices.
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.