Simultaneous temperature and magnetic field measurements using time-division multiplexing

At a Glance

Metadata	Details
Publication Date	2022-09-20
Journal	Chinese Optics Letters
Authors	Hao-Bin Lin, Ce Feng, Yang Dong, Wang Jiang, Xuedong Gao
Institutions	University of Science and Technology of China
Citations	4
Analysis	Full AI Review Included

Simultaneous Temperature and Magnetic Field Sensing via Time-Division Multiplexing: A 6CCVD Analysis

This technical documentation analyzes the research demonstrating simultaneous, decoupled temperature and magnetic field measurements using Nitrogen-Vacancy (NV) centers in diamond via a dual-microwave time-division multiplexing (TDM) protocol. This application highlights the critical need for high-quality, quantum-grade Single Crystal Diamond (SCD) materials, a core specialization of 6CCVD.

Executive Summary

This paper presents a robust quantum sensing protocol utilizing NV centers in diamond to achieve simultaneous, real-time measurement of temperature and magnetic fields.

Core Achievement: Successful implementation of a dual-microwave time-division multiplexing (TDM) protocol to decouple temperature and magnetic field signals directly.
Decoupling Mechanism: Electrical signal TDM demodulation separates the optically mixed signals, allowing Lock-In Amplifiers (LIAs) to process temperature and magnetic field information independently.
High Sensitivity: The system achieved a magnetic field sensitivity of 3.4 nT/√Hz and a temperature sensitivity of 1.3 mK/√Hz.
Enhanced Robustness: The method relies on the amplitude (R value) of the demodulated signal, making the measurement robust against phase synchronization issues and phase mismatch errors common in traditional tracking methods.
Material Requirement: The experiment utilized a small, high-quality CVD diamond sample (200 µm x 200 µm x 100 µm) with [111] crystal orientation, essential for optimizing NV properties.
Application Potential: This robust, multifunctional quantum sensing technique extends the practical applicability of NV diamond sensors in complex, noisy environments.

Technical Specifications

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

Parameter	Value	Unit	Context
Magnetic Field Sensitivity	3.4	nT/√Hz	Achieved using TDM protocol
Temperature Sensitivity	1.3	mK/√Hz	Achieved using TDM protocol
Diamond Crystal Orientation	[111]	N/A	CVD growth orientation
Diamond Dimensions	200 x 200 x 100	µm	Sample size used in the experiment
MW Resonance Frequency (Nominal)	2.87	GHz	Zero-field splitting (D) of NV ground state
ODMR Linewidth (Approx.)	8	MHz	Measured spectral width
DC Bias Magnetic Field	46	Gauss	Applied via permanent magnet
Laser Excitation Wavelength	532	nm	Used for spin initialization and readout
Signal Modulation Frequency	2.21	kHz	Used for phase-sensitive detection
LIA Time Constant	15	ms	Used during ODMR measurement

Key Methodologies

The simultaneous measurement was achieved by combining dual-frequency driving, frequency modulation, and time-division demodulation.

Material Selection: A CVD-grown diamond sample with [111] orientation (200 µm x 200 µm x 100 µm) containing NV centers was used.
Optical Setup: A 532 nm laser illuminated the diamond via a fiber. Fluorescence was collected through a composite parabolic lens (CPC) and filtered before reaching a balanced photodetector.
Magnetic Bias: A DC bias magnetic field (46 Gauss) was applied to induce Zeeman splitting, forming the basis for magnetometry.
ODMR Spectroscopy: Optically Detected Magnetic Resonance (ODMR) was performed by sweeping the MW frequency near 2.87 GHz.
TDM Protocol Implementation: Dual-frequency driving (e.g., f₁ + f₃) and frequency modulation (e.g., f₁ - f₃) were combined to minimize MW resources and enable simultaneous measurement.
MW Switching: Two MW switches (SW1, SW2) were controlled by TTL signals from a pulse generator to implement time-division multiplexing of the fluorescence signal.
Decoupled Detection: The switched signals were sent to two separate Lock-In Amplifiers (LIA1 and LIA2). LIA1 measured the temperature signal (S₁₁ - S₁₂), and LIA2 measured the magnetic field signal (S₂₁ - S₂₂).
Robust Readout: The amplitude (R value) of the demodulated signal was used for sensing, eliminating the need for phase synchronization and enhancing robustness.

6CCVD Solutions & Capabilities

6CCVD provides the high-specification MPCVD diamond materials and customization services necessary to replicate, scale, and advance this cutting-edge quantum sensing research.

Applicable Materials

To achieve the high sensitivity and long coherence times required for TDM ODMR protocols, researchers need diamond with precise control over NV concentration and crystal quality.

6CCVD Material Recommendation	Specification & Relevance to Research
Quantum Grade Single Crystal Diamond (SCD)	Optimized for high NV density and long T₂ coherence times, crucial for high-sensitivity quantum sensing applications like the 3.4 nT/√Hz reported here.
Custom Crystal Orientation	The paper used [111] oriented diamond. 6CCVD offers both standard [100] and custom [111] oriented SCD plates to maximize the projection of the NV axis onto the applied magnetic field.
Optical Grade Polishing	Required for efficient 532 nm laser coupling and fluorescence collection. 6CCVD guarantees Ra < 1 nm surface roughness on SCD, minimizing scattering losses.

Customization Potential

The experimental setup utilized a small, custom-sized diamond and an external copper wire antenna. 6CCVD’s advanced fabrication capabilities allow for significant integration and scaling improvements.

Research Requirement	6CCVD Customization Solution
Custom Dimensions	The paper used 200 µm samples. 6CCVD supplies SCD plates up to 500 µm thick and PCD wafers up to 125mm in diameter, enabling scaling to larger sensor arrays.
Integrated MW Delivery	The experiment used an external copper wire antenna. 6CCVD offers in-house metalization services (Au, Pt, Ti, Pd) for fabricating integrated Coplanar Waveguides (CPWs) directly onto the diamond surface, replacing external antennas and improving MW coupling efficiency.
Specific Thickness Control	6CCVD provides precise thickness control for SCD and PCD materials from 0.1 µm up to 500 µm, allowing researchers to optimize the sensing volume for specific TDM protocols.
Global Logistics	6CCVD offers global shipping (DDU default, DDP available), ensuring rapid and reliable delivery of custom quantum materials worldwide.

Engineering Support

The complexity of simultaneous, decoupled quantum sensing requires expert material consultation.

NV Optimization: 6CCVD’s in-house PhD team can assist researchers in optimizing the NV concentration and depth profile within the diamond substrate to maximize signal-to-noise ratio for similar TDM ODMR sensing projects.
Surface Termination: We provide consultation on surface termination (e.g., oxygen or hydrogen termination) to ensure stable NV charge state and minimize surface noise, critical for achieving the reported high sensitivities.
Protocol Extension: We offer support for material selection for extending this research to other modalities, such as using Boron-Doped Diamond (BDD) for electrochemical sensing applications.

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

View Original Abstract

Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field, temperature, and pressure. Meanwhile, sensing so many variables at the same time often introduces additional noise, causing a reduced accuracy. Here, a dual-microwave time-division multiplexing protocol is used in conjunction with a lock-in amplifier in order to decouple temperature from the magnetic field and vice versa. In this protocol, dual-frequency driving and frequency modulation are used to measure the magnetic and temperature field simultaneously in real time. The sensitivity of our system is about 3.4 nT/Hz and 1.3 mK/Hz, respectively. Our detection protocol not only enables multifunctional quantum sensing, but also extends more practical applications.

Tech Support

Original Source

DOI: https://doi.org/10.3788/col202321.011201