Wavelet-based fast time-resolved magnetic sensing with electronic spins in diamond

At a Glance

Metadata	Details
Publication Date	2016-04-29
Journal	Physical review. B./Physical review. B
Authors	Nanyang Xu, Feng-Jian Jiang, Yu Tian, Jianfeng Ye, Fazhan Shi
Institutions	Huangshan University, Hefei University of Technology
Citations	13
Analysis	Full AI Review Included

Technical Documentation: Wavelet-Based Fast Magnetic Sensing in Diamond

6CCVD Material Analysis & Sales Documentation Reference: Xu et al., Wavelet-based fast time-resolved magnetic sensing with electronic spins in diamond (arXiv:1512.07049v1)

Executive Summary

This research demonstrates a significant advancement in time-resolved magnetic sensing using Nitrogen-Vacancy (NV) centers in diamond, leveraging the Haar wavelet transform for rapid signal reconstruction.

Exponential Speed Gain: The novel Haar wavelet method reconstructs temporal magnetic signals exponentially faster, requiring only O(n) runs of the spin echo sequence compared to O(2ⁿ) runs necessary for the comparable Walsh method.
High Sensitivity: The technique maintains sensitivity comparable to the Walsh method while achieving a substantial gain over sequential Ramsey interferometry due to the use of the robust spin echo technique, which enhances the electron spin coherence time (T₂).
Robust Methodology: The reconstruction scheme is easily implemented using the standard spin echo technique, making it readily applicable to other quantum sensing systems (e.g., trapped ions, quantum dots).
Biological Application: The method successfully detects simulated nerve impulses, highlighting its potential for fast information extraction in biological sensing and quantum imaging applications.
Scalability Pathway: The authors propose scaling the technique using NV ensembles (over 10¹¹ spins in 10^-4 mm³ volume) to eliminate the need for 10⁶ signal accumulation loops, paving the way for real-time, high-speed sensing.
Material Requirement: High-purity, low-strain Single Crystal Diamond (SCD) is essential to maximize the NV center’s coherence time (T₂) and achieve the demonstrated sensitivity.

Technical Specifications

Parameter	Value	Unit	Context
Sensing Probe	NV Defect Center	N/A	Single electron spin in diamond
Reconstruction Method	Haar Wavelet Transform	N/A	Exponentially faster than Walsh method
Reconstruction Order (n)	Up to 6	N/A	N = 2ⁿ points reconstructed (max 64 points)
Required Runs (Haar)	O(n)	N/A	Exponential speed advantage
Required Runs (Walsh)	O(2ⁿ)	N/A	Resource-consuming for high orders
Total Acquisition Time	~15	minutes	For 10⁶ loops (single NV center)
Proposed Ensemble Volume	10^-4	mm³	Contains > 10¹¹ spins for faster measurement
Sensitivity Gain (Haar vs. Ramsey)	Proportional to sqrt(T₂/T₂^*)	N/A	Enhanced coherence time improves sensitivity
Detected Field Amplitude	±400 to ±2000	nT	Simulated nerve impulse signal range

Key Methodologies

The experiment relies on precise control of the NV electron spin using microwave (MW) and radiofrequency (RF) pulses applied to a high-quality diamond substrate.

Material Selection: A bulk diamond sample enriched with ¹²C was used to minimize decoherence from surrounding nuclear spins, maximizing T₂.
Spin Preparation and Readout: The NV electron spin is initialized and read out optically via a confocal microscopy system, utilizing the spin-dependent fluorescence.
Spin Echo Sequence: The standard spin echo sequence (π/2 - τ - π - τ - π/2 pulses) is implemented. This sequence acts as a controllable frequency band-pass filter, significantly extending the coherence time (T₂) compared to Ramsey interferometry.
Haar Coefficient Measurement: By associating the spin echo sequence with the Haar wavelet function, each sequence measures a specific Haar transform coefficient of the temporal magnetic field.
RF Field Generation: The time-varying magnetic field is generated using an Arbitrary Waveform Generator (RF-AWG) and radiated via a copper line placed directly on the diamond surface.
Inverse Transform: The measured Haar coefficients are processed using an inverse Haar transform to reconstruct the complete temporal magnetic signal.

6CCVD Solutions & Capabilities

6CCVD provides the high-specification MPCVD diamond materials and custom engineering services required to replicate this foundational quantum sensing research and scale it toward practical, high-speed applications like bio-magnetic imaging.

Applicable Materials for Quantum Sensing

Research Requirement	6CCVD Material Recommendation	Technical Justification
High Coherence Time (T₂)	Optical Grade Single Crystal Diamond (SCD)	Ultra-low nitrogen concentration (< 1 ppb) and minimal strain are essential for maximizing T₂, which directly determines the sensitivity of the Haar wavelet method.
Scalable Ensemble Sensing	Custom SCD Plates (up to 10mm thick)	Provides the necessary volume and purity for high-density NV creation (via implantation or in-situ doping) to achieve the proposed 10¹¹ spins/mm³ density for faster measurements.
High-Order Reconstruction	Polished SCD Substrates (Ra < 1 nm)	Extremely low surface roughness minimizes surface noise and strain effects, ensuring high fidelity for complex, multi-pulse sequences required for high-order (n > 5) Haar reconstruction.
Integrated Devices	Boron-Doped Diamond (BDD)	For future integration, BDD films can serve as highly conductive electrodes or heat sinks, compatible with on-chip RF structures.

Customization Potential for Advanced NV Sensing

The experimental setup described requires precise material engineering and integration, areas where 6CCVD excels:

Custom Dimensions: 6CCVD supplies SCD plates and wafers in custom sizes and thicknesses (SCD: 0.1µm - 500µm; Substrates: up to 10mm) to fit specific confocal or cryogenic setups.
Metalization Services: The paper utilized a copper line for RF control. 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu) and precision photolithographic patterning to integrate complex on-chip microwave and RF structures directly onto the diamond surface.
Precision Polishing: We guarantee ultra-smooth surfaces (Ra < 1 nm for SCD) crucial for minimizing surface noise and enabling high-resolution imaging applications.
Laser Cutting and Shaping: We provide custom laser cutting services to shape substrates for optimal integration with external components (e.g., waveguides or fiber coupling).

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth parameters and material selection for quantum applications. We offer consultation services to assist researchers in optimizing diamond specifications (purity, thickness, orientation) for similar Time-Resolved Magnetic Sensing projects, ensuring optimal T₂ performance and NV creation efficiency.

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

View Original Abstract

Time-resolved magnetic sensing is of great importance from fundamental\nstudies to applications in physical and biological sciences. Recently the\nnitrogen-vacancy (NV) defect center in diamond has been developed as a\npromising sensor of magnetic field under ambient conditions. However the\nmethods to reconstruct time-resolved magnetic field with high sensitivity are\nnot yet fully developed. Here, we propose and demonstrate a novel sensing\nmethod based on spin echo, and Haar wavelet transform. Our method is\nexponentially faster in reconstructing time-resolved magnetic field with\ncomparable sensitivity over existing methods. Further, the wavelet’s unique\nfeatures enable our method to extract information from the whole signal with\nonly part of the measuring sequences. We then explore this feature for a fast\ndetection of simulated nerve impulses. These results will be useful to\ntime-resolved magnetic sensing with quantum probes at nano-scales.\n

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevb.93.161117