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6CCVD Research

Construction and operation of a tabletop system for nanoscale magnetometry with single nitrogen-vacancy centers in diamond

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2020-02-01
JournalAIP Advances
AuthorsDaiki Misonou, Kento Sasaki, Shuntaro Ishizu, Yasuaki Monnai, Kohei M. Itoh
InstitutionsKeio University, RIKEN Center for Emergent Matter Science
Citations28
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”
  • Compact, COTS-Based System: A compact, tabletop quantum magnetometry system was successfully designed and constructed, relying primarily on Commercial Off-the-Shelf (COTS) optical and electronic components to ensure high reproducibility for non-specialists.
  • Single NV Resolution: The setup utilizes a confocal scanning microscope configuration with linear stages (10 nm resolution, 20 x 20 mm2 scan range) and single-mode fiber filtering, achieving single Nitrogen-Vacancy (NV) center optical resolution.
  • State-of-the-Art Sensing: The system implements advanced pulsed Optically Detected Magnetic Resonance (ODMR) protocols, including Ramsey, Hahn echo, and dynamical decoupling sequences (XYk).
  • High Coherence Achieved: Coherence times (T2) up to 364 ”s were measured for bulk NV centers in 12C-enriched diamond, enabling high-resolution spectroscopy.
  • Single Spin Detection: Demonstrated detection and full hyperfine characterization of individual 13C nuclear spins within the diamond lattice using correlation spectroscopy.
  • Nanoscale NMR: Achieved nanoscale Nuclear Magnetic Resonance (NMR) detection of ensemble proton (1H) nuclear spins placed on the diamond surface (in oil), allowing the estimation of shallow NV center depth (6.26 nm).

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
NV Center Spin StateS=1-Paramagnetic defect ground state (3A2)
Zero-Field Splitting (D)2.87GHzNV electronic spin resonance frequency
Electron Gyromagnetic Ratio (Îłe)28.0MHz/mT-
Excitation Wavelength532nmGreen laser for optical pumping
Emission Wavelength Range650 - 800nmPhonon sideband fluorescence
SPCM Detection Efficiency> 70%At 700 nm
SPCM Timing Resolution< 500ps-
Lateral Scan Range20 x 20mm2Sigma Tech linear stage
Lateral Resolution10nmMinimum step size of linear stage
Confocal Depth Resolution~1”mAchieved via single-mode fiber spatial filtering
Magnet Remanence (Br)1270 ± 20mTNdFeB N40 cylindrical magnet
Applied DC Field (B0) Range0 - 30mTControlled by magnet distance (d)
Microwave Antenna Resonance (Antenna #2)2.325GHzUsed for B0 ≈ 20 mT operation
AWG Sampling Rate1GS/sTektronix AWG7102
T2* (Ramsey Dephasing)0.50”sSingle NV center (bulk 13C diamond)
T2 (Hahn Echo Coherence)364”sSingle NV center (bulk 13C diamond)
1H Larmor Frequency (fh)1MHzAt B0 = 23.5 mT
Estimated Shallow NV Depth (dNV)6.26nmDetermined via proton NMR spectroscopy
13C Nuclear Spin Density (Natural Abundance)1.1%Lattice sites occupied by 13C
Diamond Atomic Density1.77 x 1023cm-3-
NV Density (High Quality Substrate)< 5 x 1012cm-3Required for single NV resolution

Key Methodologies

Section titled “Key Methodologies”

  1. System Construction (Confocal Microscopy):

    • The optical path uses fiber optics (laser to collimator, objective to SPCM) and an optical cage system for self-aligned free-space optics.
    • Scanning is achieved using a dual-axis linear feedback stage (x, y) and a piezo positioner (z).
    • Detection uses a Single Photon Counting Module (SPCM) coupled via a single-mode fiber, which acts as a spatial filter for confocal depth resolution.

  2. Microwave (MW) Delivery:

    • Broadband, spatially- uniform planar ring antennas (Antenna #1 or #2) are used, designed to match the required resonance frequency (fres) based on the target DC magnetic field (B0).
    • MW pulses are generated using an Arbitrary Waveform Generator (AWG) and a Vector Signal Generator (VSG) to produce phase-controlled In-phase (I) and Quadrature (Q) signals.

  3. DC Magnetic Field (B0) Control:

    • B0 is generated by a cylindrical NdFeB permanent magnet.
    • Alignment is achieved by rotating the magnet stage until B0 is parallel to a chosen NV symmetry axis ([111]), minimizing the resonance frequency (fNV) dip in the CW ODMR spectrum.
    • B0 strength is controlled by adjusting the distance (d) between the magnet and the sample using a linear actuator.

  4. Spin Manipulation and Readout:

    • Rabi Oscillation: Used to calibrate the duration of π/2 and π pulses. Square pulses are preferred for π/2 (short duration), and cosine-square pulses are used for π pulses in multipulse sequences.
    • WURST Pulses: Chirped microwave pulses (wideband, uniform rate, smooth truncation) are used for robust, adiabatic flipping of the NV spin state (ms=0 to ms=-1).
    • Phase Cycling: Used in all multipulse experiments (e.g., Hahn echo) to subtract background noise and ensure accurate setting of experimental parameters.

  5. Quantum Sensing Protocols:

    • Internal Spin Sensing (13C): Dynamical decoupling sequences (XY4-N, XY16-N) combined with Correlation Spectroscopy are used to resolve the hyperfine parameters (a||, a⊄) of individual 13C nuclear spins.
    • External Spin Sensing (1H): The XY16-64 sequence is applied to detect ensemble proton spins in oil on the diamond surface (shallow NV centers), allowing the determination of the NV depth (dNV) based on the signal decay envelope.

Commercial Applications

Section titled “Commercial Applications”
  • Quantum Computing and Networks: The system serves as a robust platform for developing and testing quantum control sequences, crucial for realizing solid-state qubits and optically interfaced quantum networks.
  • Nanoscale NMR Spectroscopy: Enables chemical analysis and structural determination of extremely small sample volumes (zeptoliters), benefiting pharmaceutical research, materials science, and surface chemistry studies.
  • Biological Imaging (NanoMRI): Potential application in high-resolution Magnetic Resonance Imaging of single proteins or biological processes, offering chemical resolution under ambient (room temperature) conditions.
  • Advanced Materials Characterization: Used for quality control and optimization of diamond substrates, particularly those prepared via Chemical Vapor Deposition (CVD) or ion implantation, by characterizing NV center density, depth, and coherence properties.
  • High-Sensitivity Magnetometry: Provides a foundation for developing portable or integrated magnetometers capable of detecting magnetic fields with nanotesla sensitivity.
View Original Abstract

A single nitrogen-vacancy (NV) center in diamond is a prime candidate for a solid-state quantum magnetometer capable of detecting single nuclear spins with prospective application to nuclear magnetic resonance (NMR) at the nanoscale. Nonetheless, an NV magnetometer is still less accessible to many chemists and biologists as its experimental setup and operational principle are starkly different from those of conventional NMR. Here, we design, construct, and operate a compact tabletop-sized system for quantum sensing with a single NV center, built primarily from commercially available optical components and electronics. We show that our setup can implement state-of-the-art quantum sensing protocols that enable the detection of single 13C nuclear spins in diamond and the characterization of their interaction parameters, as well as the detection of a small ensemble of proton nuclear spins on the diamond surface. This article provides extensive discussions on the details of the setup and the experimental procedures, and our system will be reproducible by those who have not worked on the NV centers previously.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - Quantum sensing [Crossref]
  2. 2008 - Nanoscale magnetic sensing with an individual electronic spin in diamond [Crossref]
  3. 2008 - Nanoscale imaging magnetometry with diamond spins under ambient conditions [Crossref]
  4. 2014 - Magnetometry with nitrogen-vacancy defects in diamond [Crossref]
  5. 2014 - Nitrogen-vacancy centers in diamond: Nanoscale sensors for physics and biology [Crossref]
  6. 2018 - Probing condensed matter physics with magnetometry based on nitrogen-vacancy centres in diamond [Crossref]
  7. 2018 - Tutorial: Magnetic resonance with nitrogen-vacancy centers in diamond—microwave engineering, materials science, and magnetometry [Crossref]
  8. 2013 - Nanoscale nuclear magnetic resonance with a nitrogen-vacancy spin sensor [Crossref]
  9. 2013 - Nuclear magnetic resonance spectroscopy on a (5-nanometer)3 sample volume [Crossref]
  10. 2014 - Nuclear magnetic resonance spectroscopy with single spin sensitivity [Crossref]

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