Robust Noise Suppression and Quantum Sensing by Continuous Phased Dynamical Decoupling

At a Glance

Metadata	Details
Publication Date	2025-03-26
Journal	Physical Review Letters
Authors	Daniel Louzon, Genko T. Genov, Nicolas Staudenmaier, Florian Frank, Johannes Lang
Institutions	Element Six (Germany), Paris Centre for Quantum Technologies
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Robust Quantum Sensing via CPDD

This document analyzes the research demonstrating Continuous Phased Dynamical Decoupling (CPDD) using Nitrogen-Vacancy (NV) centers in diamond, highlighting the critical material requirements and positioning 6CCVD’s capabilities as the ideal solution for replicating and advancing this high-precision quantum sensing technology.

Executive Summary

The research successfully introduces Continuous Phased Dynamical Decoupling (CPDD) as a robust method for quantum sensing, particularly effective in environments where pulsed decoupling is challenging (e.g., high magnetic fields, limited driving power).

Core Achievement: Demonstrated nanoscale high-frequency sensing (nano-NMR) using single NV centers in diamond, achieving microhertz frequency uncertainty.
Precision: Achieved a frequency uncertainty of 28 µHz over a 120 s measurement time by combining CPDD with Quantum Heterodyne Detection (Qdyne).
Robustness: CPDD (using the CXY8 sequence) showed robustness improved by more than 20 times against amplitude noise compared to conventional Continuous Dynamical Decoupling (CDD).
Methodological Advantage: CPDD relies on precise control of phase change timing (T), which is experimentally easier and more accurate than controlling the Rabi frequency ($\Omega$) required by standard CDD.
Material Requirement: The success hinges on the use of high-purity, isotopically enriched ¹²C Single Crystal Diamond (SCD) to maximize spin coherence times ($T_2$).
6CCVD Value Proposition: 6CCVD specializes in providing the necessary high-purity, isotopically enriched SCD substrates and custom metalization services required for next-generation NV-based quantum devices.

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on the performance metrics and key operational parameters.

Parameter	Value	Unit	Context
Frequency Uncertainty ($\delta\nu_0$)	28	µHz	Achieved over 120 s measurement time
Amplitude Sensitivity ($\eta_B$)	118 ± 8	nT/√Hz	High-frequency sensing regime
Frequency Sensitivity ($\eta_{\nu_0}$)	32	mHz/Hz^3/2	CXY8 sequence with Qdyne
Rabi Frequency ($\Omega$)	2$\pi$ 8	MHz	Driving field frequency (Resonance condition $\Omega = \omega_1$)
Signal Frequency ($\omega_1$)	2$\pi$ 8.005	MHz	Hydrogen Larmor frequency (High field)
Phase Change Interval (T)	62.5	ns	Used for $\Omega = 2\pi$ 8 MHz
Bias Magnetic Field ($B_z$)	1882 ± 3	G	High field experiment
Diamond Isotopic Purity	99.999	%	¹²C enrichment
NV Center Depth	≈10	nm	Shallow NV center required for nanoscale NMR
Robustness Improvement	>20	Times	CXY8 vs. CX (standard CDD)

Key Methodologies

The experiment relies on precise material engineering and advanced microwave control techniques to achieve robust decoupling and high-resolution sensing.

Material Selection: Used isotopically enriched ¹²C Single Crystal Diamond (99.999% purity) to minimize decoherence caused by ¹³C nuclear spins.
NV Center Creation: Shallow NV centers (depth ≈10 nm) were utilized to maximize coupling to the external hydrogen nuclear spin bath (nano-NMR signal).
Magnetic Environment: A permanent neodymium magnet was used to apply an external magnetic bias field ($B_z$) aligned with the NV axis (up to 1882 G).
Microwave Delivery: A copper wire placed on the diamond surface was used to generate the microwave driving field ($\Omega$).
Sequence Generation: An Arbitrary Waveform Generator (AWG) was employed for direct generation of the CPDD sequences (CXY8), ensuring precise control over the phase changes at intervals $T = \pi/\Omega$.
Sensing Protocol: The CXY8 sequence was combined with Quantum Heterodyne Detection (Qdyne) to achieve phase-sensitive, high-resolution frequency measurement.
Readout: A green laser (518 nm) was used for NV initialization and spin-dependent fluorescence readout.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the foundational diamond materials and custom engineering services required to replicate and extend the high-performance quantum sensing demonstrated in this research.

Applicable Materials

The microhertz precision achieved is directly dependent on maximizing the coherence time ($T_2$) of the NV center, which necessitates ultra-high purity diamond.

Material Requirement (Paper)	6CCVD Solution	Technical Specification
Ultra-high Purity Substrate	Optical Grade Single Crystal Diamond (SCD)	Low strain, high crystalline quality
Isotopic Enrichment	Isotopically Enriched ¹²C SCD	Purity up to 99.999% available for maximum $T_2$
NV Center Host	Low Nitrogen Concentration SCD	Optimized for subsequent NV creation (implantation or delta-doping)
Substrate Size	Custom SCD Plates/Wafers	Standard and custom dimensions available

Customization Potential

The experiment relies on precise surface preparation and integrated microwave delivery structures. 6CCVD provides end-to-end material customization to facilitate device fabrication.

Surface Preparation: The use of shallow NV centers (≈10 nm) demands exceptional surface quality. 6CCVD provides Ultra-Low Roughness Polishing for SCD substrates, achieving Ra < 1 nm, which is critical for high-fidelity NV creation and minimizing surface noise.
Custom Dimensions: We supply SCD plates and wafers in custom dimensions and thicknesses (0.1 µm to 500 µm) tailored for specific experimental setups and integration into cryostats or high-field magnets.
Integrated Microwave Structures: The paper used a copper wire for driving. 6CCVD offers In-House Custom Metalization services (Au, Pt, Pd, Ti, W, Cu) to deposit high-conductivity thin films directly onto the diamond surface, enabling lithographically defined, high-precision microwave antennas and transmission lines for optimized Rabi frequency control.

Engineering Support

6CCVD’s technical sales team and in-house PhD material scientists are experts in optimizing diamond properties for quantum applications.

Material Consultation: We assist researchers in selecting the optimal diamond specifications (e.g., nitrogen concentration, isotopic purity, crystal orientation) required to maximize $T_2$ and $T_1$ coherence times for similar Nanoscale Quantum Sensing and Magnetometry projects.
Process Integration: We provide technical guidance on how our substrates integrate with post-growth processing steps, such as ion implantation for shallow NV creation and surface termination for device stability.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond materials to research facilities worldwide.

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

View Original Abstract

We propose and demonstrate experimentally continuous phased dynamical decoupling (CPDD), where we apply a continuous field with discrete phase changes for quantum sensing and robust compensation of environmental and amplitude noise. CPDD does not use short pulses, making it particularly suitable for experiments with limited driving power or nuclear magnetic resonance at high magnetic fields. It requires control of the timing of the phase changes, offering much greater precision than the Rabi frequency control needed in standard continuous sensing schemes. We successfully apply our method to nanoscale nuclear magnetic resonance and combine it with quantum heterodyne detection, achieving microhertz uncertainty in the estimated signal frequency for a 120 s measurement. Our Letter expands significantly the applicability of dynamical decoupling and opens the door for a wide range of experiments, e.g., in nitrogen-vacancy centers, trapped ions, or trapped atoms.

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevlett.134.120802