Atomic-Scale Positioning of Single Spins via Multiple Nitrogen-Vacancy Centers

At a Glance

Metadata	Details
Publication Date	2016-04-25
Journal	Physical Review Applied
Authors	Wen-Long Ma, Shu-Shen Li, Geng-yu Cao, Ren-Bao Liu, Wen-Long Ma
Institutions	Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences
Citations	5
Analysis	Full AI Review Included

Technical Documentation and Analysis: Atomic-Scale Spin Positioning via Multiple NV Centers

Executive Summary

This research introduces a novel multi-sensor scheme utilizing multiple Nitrogen-Vacancy (NV) centers embedded in a diamond tip to achieve sub-nanometer resolution in single electron spin positioning. This advancement is critical for next-generation nanoscale magnetometry and single-molecule structure analysis.

Atomic Resolution Achieved: The proposed method demonstrated spatial resolution better than 0.3 nm in simulation, enabling atomic-scale positioning of a target electron spin 4-20 nm away.
Multi-Sensor GPS Analog: Three closely spaced NV centers (separated by 6-7 nm) act as independent sensors, leveraging characteristic electron spin-coherence oscillations (fingerprints) to triangulate the target spin’s 3D coordinates, analogous to GPS.
Enhanced Speed and Efficiency: The scheme eliminates the need for time-consuming variations of magnetic field orientation or nanometer-step spatial scanning required by single-NV sensor methods.
Coherence Engineering: The Carr-Purcell-Meiboom-Gill (CPMG) dynamical decoupling sequence is essential for suppressing background ¹³C nuclear spin bath noise while selectively amplifying the weak signal from the remote target spin.
Material Requirement: Achieving the necessary long spin coherence times (T₂ > 100 µs required for extended detection range) mandates the use of ultra-high-purity, low-strain, Single Crystal Diamond (SCD) substrates to minimize decoherence sources.
Core Method: Positioning is achieved by matching the time-domain coherence oscillation features (dips and peaks) against a pre-established fingerprint library, significantly accelerating detection.

Technical Specifications

The following hard data points were extracted from the simulations and theoretical models detailing the physical requirements and demonstrated capabilities of the multi-NV positioning scheme.

Parameter	Value	Unit	Context
Spatial Resolution	< 0.3	nm	Achieved in simulation using a fingerprint matching library.
Detection Range (Short)	4 - 10	nm	Demonstrated using CPMG-30 sequence.
Detection Range (Extended)	~20	nm	Demonstrated using CPMG-100 sequence.
NV Sensor Spacing	6 - 7	nm	Required distance between NV-A, NV-B, and NV-C for independent addressing.
Strain Anisotropy (ε)	2 - 4	MHz	Required difference in local strain to individually address the three NV centers. (ε_A=3, ε_B=2, ε_C=4 MHz).
Magnetic Field (B)	0.1	Gauss	Applied along the [111] axis for short-range detection (comparable to dipolar interaction).
CPMG Pulse Count (N)	30 / 100	N	Controls noise frequency amplification and detection range.
Target T₂ Requirement	> 100	µs	Necessary coherence time for the target spin to enable extended 20 nm detection range using CPMG-100.
Diamond Surface Depth	1 - 10	nm	Optimal depth range for shallow NV centers used in nanoscale sensing.

Key Methodologies

The experiment relies heavily on precise material control, specialized defect engineering, and advanced quantum control sequences.

High-Purity Single Crystal Diamond (SCD) Substrate:
- Use of isotopically engineered diamond (ultra-low ¹³C natural abundance) is critical to prolong the NV center T₂ coherence time by suppressing the nuclear spin bath, enabling effective Dynamical Decoupling (DD).
NV Center Generation and Positioning:
- Creation of multiple, closely spaced NV sensors (6-7 nm apart) near the diamond surface (1-10 nm depth). Techniques include nitrogen ion implantation (e.g., ¹⁵N²⁺, N₃, N₄ molecules) followed by high-temperature annealing.
Strain and Addressability Control:
- Ensuring slight differences in local strain-induced transverse anisotropy (ε ≈ 2-4 MHz) for each NV center (A, B, C). This strain variance allows individual optical or microwave addressing of the sensors.
Quantum Control (CPMG Sequence):
- Application of the N-pulse Carr-Purcell-Meiboom-Gill (CPMG-N) sequence to the NV electron spin. This simultaneously suppresses low-frequency background noise (from the ¹³C bath and other NV sensors) while resonantly amplifying the weak dipolar interaction signal from the distant target spin.
Data Acquisition and Positioning:
- Measuring the spin coherence profile of each of the three NV centers separately. The characteristic oscillation patterns (coherence dips/peaks) are compared to a pre-calculated “fingerprint library” (discretized by distance R and angle θ) to determine the 3D coordinates (R_i, θ_i) of the target spin with sub-nanometer precision.

6CCVD Solutions & Capabilities: Enabling Atomic-Scale Quantum Sensing

6CCVD is positioned as the ideal partner to supply the specialized diamond materials required to replicate and advance this cutting-edge quantum magnetometry research. Our capabilities directly address the foundational material needs for high-coherence NV sensor platforms.

Applicable Materials

To achieve the long coherence times (T₂) and low noise required for CPMG-N sequences (N=100+), researchers require ultra-high-purity, low-strain SCD, often with controlled isotopic composition.

6CCVD Material Solution	Description and Application	Relevance to Research
Optical Grade Single Crystal Diamond (SCD)	Ultra-high purity, low nitrogen (PPM level control), and extremely low concentration of background defects. Ideal base material for quantum applications.	CRITICAL: Minimizes unwanted intrinsic defects that limit T₂ time, ensuring superior spin coherence necessary for detection range extension (up to 20 nm).
Isotopically Purified SCD (Low ¹³C)	SCD wafers with depleted ¹³C content (< 0.1%).	ESSENTIAL: Directly suppresses the dominant decoherence source (the ¹³C nuclear spin bath), maximizing NV center T₂, allowing successful dynamical decoupling (CPMG).
N-Doped SCD Substrates	Single crystal substrates with controlled, uniform nitrogen doping, suitable for subsequent NV creation (e.g., via irradiation/annealing).	Provides the necessary host nitrogen atoms for creating the multiple, shallow NV centers required for the multi-sensor scheme.

Customization Potential for NV Sensor Platforms

The research necessitates specific geometries (diamond tip probes) and the integration of microwave control circuits. 6CCVD offers comprehensive in-house engineering services to meet these demands.

Custom Dimensions and Geometry: 6CCVD provides laser cutting and shaping services to produce substrates with custom dimensions (up to 125mm PCD/SCD) and non-standard geometries, including preparation of small diamond chips or probe tips required for this multi-sensor detection scheme.
Ultra-Polished Surface Finish: We guarantee Ra < 1 nm polishing on SCD wafers. A pristine surface is vital for enabling precise control over the depth (1-10 nm) and stability of the shallow NV centers used for high-resolution sensing.
In-House Metalization for Qubit Control: Implementing the CPMG pulse sequences requires on-chip microwave delivery structures. 6CCVD offers custom thin-film metalization, including Au, Pt, Ti, W, and Cu, allowing researchers to integrate microwave transmission lines or micro-coil structures directly onto the SCD surface for efficient manipulation of the NV electron spins.
Thickness Control: We supply SCD substrates up to 500 µm thick, providing the robust mechanical support necessary for creating and handling microfabricated diamond tips.

Engineering Support

The successful replication and extension of this atomic-scale positioning technique relies on precise control over material growth, defect introduction, and electrical/magnetic parameters (strain engineering, B-field orientation).

6CCVD’s in-house PhD team provides specialized engineering consultation on:

Material Selection: Guiding the choice between standard SCD and isotopically purified diamond based on target coherence time (T₂) requirements for advanced quantum sensing applications.
Substrate Preparation: Consulting on ideal surface preparation, orientation, and nitrogen doping levels prior to implantation or etching processes used to create shallow, high-quality NV centers.
Strain Management: Advising on material properties and post-processing techniques (e.g., specific annealing protocols or controlled doping) that influence the local strain parameters (ε) crucial for individually addressing multiple NV centers in a compact structure.

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

View Original Abstract

We present a scheme of positioning a single electron spin with sub-nanometer\nresolution through multiple nitrogen-vacancy centers in diamond. With unwanted\nnoise suppressed by dynamical decoupling, the spin coherence of each center\ndevelops characteristic oscillations due to a single electron spin located\n$4{\sim20}$ nm away from the centers. We can extract the position information\nfrom the characteristic electron spin-coherence oscillations of each center.\nThis scheme is useful for high-resolution nanoscale magnetometry and spin-based\nquantum computing.\n

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevapplied.5.044016

References

1990 - Principles of Nuclear Magnetic Resonance in One and Two Dimensions [Crossref]