Narrow-bandwidth sensing of high-frequency fields with continuous dynamical decoupling

At a Glance

Metadata	Details
Publication Date	2017-10-18
Journal	Nature Communications
Authors	Alexander Stark, Nati Aharon, Thomas Unden, Daniel Louzon, Alexander Hück
Institutions	Technical University of Denmark, Universität Ulm
Citations	65
Analysis	Full AI Review Included

Technical Documentation and Analysis: High-Frequency Quantum Sensing via Continuous Dynamical Decoupling in Diamond

This documentation analyzes the key technical achievements outlined in the attached research regarding the use of Continuous Dynamical Decoupling (CDD) in Nitrogen-Vacancy (NV) centers in diamond for high-frequency magnetic field sensing.

Executive Summary

6CCVD provides the high-purity single crystal diamond (SCD) materials essential for replicating and extending this breakthrough quantum sensing research. The paper demonstrates a robust protocol integrating CDD into high-frequency metrology, overcoming limitations of standard pulsed methods.

Core Breakthrough: Successful integration of Continuous Dynamical Decoupling (CDD) into NV-diamond sensing schemes for high-frequency AC fields (up to 1.6 GHz).
Material Basis: The method relies on the stability and coherence properties of the Nitrogen-Vacancy (NV) center in a natural abundance ¹³C diamond matrix.
Performance Metrics: Achieved a coherence time ($T_2$) of 1.43 ms under double-drive CDD—an improvement of over one order of magnitude compared to single-drive protocols.
Sensitivity: Demonstrated an optimal sensitivity of $\leq 1 \mu$T Hz^-0.5 at 1.6 GHz, enabling the detection of weak high-frequency signals with magnetic field amplitudes as low as $\approx 4$ nT.
Scalability & Future Potential: The generic scheme is applicable across various solid-state, molecular, and atomic two-level systems (TLS), with potential scalability to high-frequency sensing tasks up to the THz range.
6CCVD Value Proposition: 6CCVD specializes in custom SCD substrates with specified nitrogen (N) concentration control and superior surface finishes (Ra < 1 nm) necessary for maximizing NV creation efficiency and ensuring maximum quantum coherence.

Technical Specifications

The following hard data was extracted, summarizing the performance and operational parameters of the high-frequency sensing scheme utilizing concatenated CDD.

Parameter	Value	Unit	Context
Coherence Time (T₂)	1.43 $\pm$ 0.17	ms	Achieved with Double Drive (Concatenated CDD)
Coherence Time Improvement	> 1	Order of Magnitude	Compared to single drive (193 $\mu$s)
Sensing Bandwidth Improvement	$\approx 3$	Orders of Magnitude	Compared to standard relaxometry approach
Optimal Sensitivity ($\eta$)	$\leq 1$	$\mu$T Hz^-0.5	Achieved with Double Drive at 1.6 GHz
Baseline Sensitivity ($\eta$)	$\leq 20$	$\mu$T Hz^-0.5	Single Drive approach
Smallest Detectable Field ($\delta B_{\min}$)	$\approx 4$	nT	Weak high-frequency signal detection
Drive Field 1 Frequency ($\Omega_1/2\pi$)	3.363	MHz	Rabi frequency used in Concatenated CDD
Drive Field 2 Frequency ($\Omega_2/2\pi$)	505	kHz	Rabi frequency used in Concatenated CDD
Initialization/Readout Wavelength	532	nm	Standard NV optical excitation

Key Methodologies

The experimental scheme successfully combines advanced MPCVD diamond substrate preparation with sophisticated microwave manipulation techniques to achieve unprecedented coherence times for AC field sensing.

Diamond Material Selection: Utilized a diamond sample with the natural abundance of carbon ¹³C, leveraging the Nitrogen-Vacancy (NV) center’s ground sub-levels as the two-level quantum sensor system (TLS).
Optical Initialization and Readout: Used a 532 nm laser system to initialize and perform spin-dependent fluorescence measurements of the NV center states.
Qubit Control: Manipulated the NV center spin states using external microwave (MW) fields, delivered via transmission lines proximate to the diamond surface.
Concatenated Continuous Dynamical Decoupling (CDD): Applied two phase-matched continuous driving fields ($\Omega_1$ and $\Omega_2$) to create a highly robust, doubly dressed qubit state.
Frequency Matching: Tuned the NV center’s energy gap ($\omega_0$) using a DC magnetic field (DC magnet) to match the high-frequency external signal ($\omega_s$).
Signal Integration: Demonstrated that the external signal itself acts partially as a decoupling drive, which further prolongs the sensor’s coherence time and enhances sensitivity.
Performance Quantification: Measured the sensitivity ($\delta B_{\min}$) by recording signal-induced Rabi oscillations in the robust qubit subspace, demonstrating coherence time limited by the sensor lifetime ($T_1$).

6CCVD Solutions & Capabilities

This quantum sensing protocol critically relies on the quality and engineering specification of the MPCVD diamond substrate. 6CCVD is uniquely positioned to supply the materials and processing required for both replicating this research and scaling its application.

Applicable Materials

To achieve lifetime-limited coherence (T₂ $\approx$ T₁/2) and superior NV performance, researchers require ultra-high purity diamond with controlled intrinsic defects.

Material Recommendation: High-Purity Electronic Grade Single Crystal Diamond (SCD).
- Purity: SCD is crucial for minimizing background noise and maximizing the $T_2$ coherence time. We offer materials optimized for extremely low paramagnetic nitrogen content (low P1 centers).
- NV Engineering: While the paper used natural abundance ¹³C diamond, 6CCVD can supply specialized SCD substrates where nitrogen concentration is strictly controlled during growth to optimize the yield and quality of NV centers near the surface.
- Thickness Control: We provide SCD plates in the ideal thickness range (e.g., 50 $\mu$m to 500 $\mu$m), allowing optimization for microwave penetration depth and heat dissipation.

Customization Potential

The integration of microwave control fields ($\Omega_1, \Omega_2$) and optical readout requires tight geometric tolerances and specialized surface modification.

Requirement	6CCVD Capability	Technical Advantage
Surface Finish	Ultra-Low Roughness Polishing (Ra < 1 nm for SCD)	Essential for high-quality optical readout (532 nm laser) and minimizing scattering, critical for high-contrast fluorescence measurements.
Microwave Circuitry	Custom Metalization Services (Ti, Pt, Au, Cu, W)	We provide high-fidelity metal deposition for fabrication of microwave waveguides and transmission lines (e.g., coplanar waveguides or striplines) directly onto the diamond, ensuring minimal signal loss for the $\Omega_1$ and $\Omega_2$ drives.
Device Geometry	Custom Dimensions and Shaping	We offer SCD and large PCD plates up to 125mm in size, along with precision laser cutting to create custom chip geometries necessary for integrating the DC magnet and MW drives (Fig. 1a, b).
Advanced Doping	Boron-Doped Diamond (BDD)	For future research requiring integrated conductivity or electrochemical sensing alongside NV centers, 6CCVD offers highly uniform BDD films.

Engineering Support

NV-diamond quantum sensing is a complex field where material specifications are intrinsically linked to quantum performance metrics.

Coherence Optimization: 6CCVD’s in-house PhD material science team specializes in tailoring MPCVD recipes to optimize substrate properties specifically for demanding Quantum Sensing and Metrology projects. This includes achieving targeted isotopic purity (e.g., ¹²C enrichment) or controlling nitrogen concentration for maximizing $T_2$.
Scaling Applications: The researchers noted potential application across THz sensing fields. 6CCVD can assist engineers in selecting appropriate large-area PCD substrates (up to 125mm) for scaling up device fabrication while maintaining required thermal and mechanical properties.
Global Logistics: We ensure reliable global shipping, managing DDU default and DDP customs processes to minimize delay for time-sensitive research projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41467-017-01159-2