Light dark matter search with nitrogen-vacancy centers in diamonds
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-03-12 |
| Journal | Journal of High Energy Physics |
| Authors | So Chigusa, M. Hazumi, Ernst David Herbschleb, Norikazu Mizuochi, Kazunori Nakayama |
| Institutions | Lawrence Berkeley National Laboratory, University of California System |
| Citations | 4 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research proposes a highly sensitive, novel approach for the direct detection of light bosonic dark matter (DM), such as axions and dark photons, utilizing nitrogen-vacancy (NV) center ensembles in diamond.
- Core Value Proposition: NV center magnetometry is leveraged to detect the effective oscillating magnetic field (Beff) generated by DM coupling to the electron spin.
- Projected Sensitivity: The estimated sensitivity for the axion-electron coupling (gaee) and dark photon kinetic mixing parameter (ε) is projected to surpass current experimental and observational limits in specific mass ranges.
- Methodology: Both DC magnetometry (Ramsey sequence) and AC magnetometry (Hahn-echo sequence) protocols are employed to optimize detection across a wide spectrum of DM masses/frequencies.
- High-Density Ensembles: Achieving the highest sensitivity requires large ensembles (up to N = 1020 NV centers) within large diamond volumes (103 cm3), necessitating advanced diamond synthesis techniques.
- Coherence Time Utilization: AC magnetometry benefits from significantly extended transversal coherence times (T2), allowing for filtering of low-frequency noise and enhancing sensitivity for higher DM frequencies.
- Resonance Search: The technique is particularly effective in a narrow-band resonance search regime where the DM mass (m) matches the NV center spin energy gap (ω+), providing a large signal enhancement factor (up to 2 x 104).
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Center Concentration (Target) | 1.6 x 1017 | cm-3 | Required for N = 1020 ensemble setup. |
| Required Diamond Volume (N=1020) | 103 | cm3 | Volume needed to achieve N = 1020 NV centers. |
| Zero-Field Splitting (D) | 2.87 | GHz | Intrinsic NV center spin triplet energy gap. |
| Energy Gap (ω+) | ~10 | µeV | Energy gap relevant for the resonance search regime. |
| Typical Free Precession Time (τ) | 0.5 | µs | Used for sensitivity estimation in the plots. |
| Spin Dephasing Time (T2*) | ~1 | µs | Limiting factor for DC magnetometry (Ramsey sequence). |
| Transversal Coherence Time (T2) | ~50 | µs | Current state-of-the-art for AC magnetometry (Hahn-echo). |
| Longest Coherence Time (T1) | 50 | s | Current longest longitudinal coherence time (used for high-mass AC sensitivity envelopes). |
| Dark Matter Velocity (vDM) | 10-3 | (unitless) | Typical DM velocity around Earth. |
| Local DM Energy Density (ρDM) | 0.4 | GeV/cm3 | Standard estimate for local DM density. |
| Estimated Effective Magnetic Field (Beff) | 1.3 x 10-8 | T | Estimated magnitude of DM-induced field (for vDM = 10-3). |
| Optimal T2/τ Ratio (DC) | T2/2 | (unitless) | Optimal choice for maximizing DC sensitivity. |
Key Methodologies
Section titled “Key Methodologies”The detection relies on measuring the phase shift (φ) induced in the NV electron spin Bloch vector by the effective dark matter magnetic field (Beff).
1. DC Magnetometry (Ramsey Sequence)
Section titled “1. DC Magnetometry (Ramsey Sequence)”The Ramsey sequence is used primarily for low-frequency dark matter signals where the oscillation period is much longer than the free precession time (τ).
- Initialization: The NV electron spin is prepared in the ground state |0>.
- First π/2 Pulse: A microwave pulse is applied, creating a superposition state of |0> and |+>.
- Free Precession: The spin evolves for duration τ (typically limited by T2* ~ 1 µs), accumulating a phase shift φ proportional to the magnetic field component Bz.
- Second π/2 Pulse: A final pulse is applied to convert the accumulated phase information into a measurable population difference.
- Signal Measurement: The relative population (S) between |+> and |0> is measured via fluorescence light, where S is proportional to sin(φ).
- Sensitivity Limit: Sensitivity is fundamentally limited by the spin projection noise (ΔSsp) and the short T2* time.
2. AC Magnetometry (Hahn-Echo Sequence)
Section titled “2. AC Magnetometry (Hahn-Echo Sequence)”The Hahn-echo sequence is used for higher-frequency dark matter signals (f > 1/τ) and to extend the coherence time (T2 >> T2*).
- Pulse Sequence: The sequence involves an initial π/2 pulse, followed by a π pulse at the midpoint (τ/2), and a final π/2 pulse at time τ.
- Noise Cancellation: The central π pulse reverses the evolution, canceling the phase accumulation from static (DC-like) magnetic impurities and low-frequency environmental noise.
- Signal Accumulation: The sequence remains sensitive to time-dependent signals (like oscillating DM fields) that change phase during the sequence.
- Signal Extraction: The signal S is proportional to sin(Δφ), where Δφ is the difference in phase accumulated during the two halves of the precession period.
3. Dark Matter Signal Extraction
Section titled “3. Dark Matter Signal Extraction”- Off-Resonance Search: For DM masses m where mτ is less than 1, the signal is extracted by measuring the broadening of the signal distribution width, √(S2), over many measurements (tobs).
- Resonance Search: When the DM mass m is tuned to the NV energy gap ω+, the interaction is enhanced by a factor proportional to τ/Δω, requiring a narrow-band search by scanning the bias magnetic field B0.
- Shielding Consideration: For dark photon detection, magnetic shielding (conductor material) is critical. The sensitivity peak shifts based on the shield size (L), with unshielded detection relying on the Earth’s radius (L ~ 6 x 103 km) as the effective shield size.
Commercial Applications
Section titled “Commercial Applications”The proposed dark matter search leverages advanced quantum sensing technology based on NV centers, which has broad commercial and scientific applications:
- Quantum Sensing and Metrology:
- Development of ultra-high-sensitivity magnetometers for room-temperature operation.
- Nanoscale magnetic imaging for materials characterization and failure analysis in electronics.
- Advanced Diamond Synthesis:
- Techniques for growing large-volume, high-purity single-crystal diamonds (103 cm3 scale) with controlled, high concentrations of NV centers.
- Methods for achieving perfect preferential orientation of NV centers for optimized vector magnetometry.
- Bioscience and Medical Diagnostics:
- High-resolution magnetic detection for mapping neural activity (single-neuron action potentials).
- Development of compact, high-sensitivity magnetic resonance systems (NMR/MRI).
- Fundamental Physics Research:
- Probing exotic spin-dependent interactions and new forces at micrometer scales.
- Serving as a platform for testing quantum entanglement protocols in solid-state systems.
View Original Abstract
A bstract We propose an approach to directly search for light dark matter, such as the axion or the dark photon, by using magnetometry with nitrogen-vacancy centers in diamonds. If the dark matter couples to the electron spin, it affects the evolution of the Bloch vectors consisting of the spin triplet states, which may be detected through several magnetometry techniques. We give several concrete examples with the use of dc and ac magnetometry and estimate the sensitivity on dark matter couplings.