Skip to content
6CCVD Research

Polarization- and frequency-tunable microwave circuit for selective excitation of nitrogen-vacancy spins in diamond

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2016-10-31
JournalApplied Physics Letters
AuthorsJohannes Herrmann, Marc A. Appleton, Kento Sasaki, Yasuaki Monnai, Tokuyuki Teraji
InstitutionsNational Institute for Materials Science, Keio University
Citations40
AnalysisFull AI Review Included

Technical Documentation and Analysis: High-Purity Diamond for Arbitrarily Polarized NV Spin Control

Section titled “Technical Documentation and Analysis: High-Purity Diamond for Arbitrarily Polarized NV Spin Control”

This document analyzes the research paper “Polarization- and frequency-tunable microwave circuit for selective excitation of nitrogen-vacancy spins in diamond” to highlight the required material specifications and demonstrate how 6CCVD’s expertise in Microwave Plasma Chemical Vapor Deposition (MPCVD) diamond fabrication directly supports and enhances this advanced quantum research.

Executive Summary

Section titled “Executive Summary”

The reported research successfully developed a novel planar microwave (MW) resonator circuit compatible with NV center quantum control, addressing critical challenges in achieving selective spin excitation.

  • Near-Perfect Polarization Control: Achieved 99% purity in selective excitation of NV spins (ms = 0 ↔ ±1 transitions) using arbitrarily polarized, in-plane oscillating magnetic fields (Bac).
  • Optimal Substrate Compatibility: The design is fully compatible with preferred (111)-oriented synthetic single crystal diamond (SCD) and allows for the critical orthogonality between the static magnetic field (Bdc) and Bac.
  • Wide Frequency Tunability: Demonstrated MW frequency tunability from 2.0 GHz to 3.2 GHz using reverse-biased varactor diodes, significantly extending operational bandwidth beyond the circuit’s intrinsic Quality factor (Q).
  • Spacial Uniformity: Generated a spatially uniform Bac distribution over a circular area (4 mm diameter), essential for ensemble NV center experiments and metrology.
  • High-Fidelity Method: Verified results using high-power pulsed Optically Detected Magnetic Resonance (ODMR) and Fast Fourier Transformation (FFT) for Rabi oscillation analysis, confirming high accuracy through simulation matching.
  • Core Material Requirement: The success hinges on the use of high-quality, specified-orientation (111) SCD substrates for advanced quantum metrology applications.

Technical Specifications

Section titled “Technical Specifications”

Key material, operational, and performance parameters extracted from the research paper.

ParameterValueUnitContext
Diamond Crystal Orientation(111)N/AEssential for selective NV center alignment
Diamond Substrate Dimensions2.5 x 2.5 x 0.5mmÂłSample used for ODMR testing (Type Ib)
Static Magnetic Field (Bdc)1.9mTApplied along the [111] quantization axis
Initial Resonance Frequency (fres)2.806GHzMeasured using fixed 1.1 pF capacitors
Tunable Frequency Range (Maximum)2.0 to 3.2GHzAchieved using varactor diodes
Quality Factor (Q)17N/ACorresponding to 165 MHz FWHM bandwidth
MW Polarization Purity99%Purity estimation for selective spin excitation
Microwave Input Power (Pmw) Range3.33 to 4.56WUsed for pulsed Rabi oscillation measurements
Simulated Oscillating Field (Bac)0.049mTInside diamond at Pmw = 4.56 W
Copper Film Thickness35”mPlanar stripline fabrication
Varactor Diode Bias Voltage Range1.5 to 15VControls capacitance for frequency tuning

Key Methodologies

Section titled “Key Methodologies”

A concise, ordered list detailing the core fabrication and experimental techniques utilized to achieve tunable, polarized microwave fields.

  1. Resonator Fabrication: A planar microwave resonator was constructed using a copper stripline ring cavity architecture on an epoxy glass substrate (T = 1.6 mm, t = 35 ”m copper films), connected symmetrically to four input/termination ports.
  2. Simulation & Optimization: Three-dimensional electromagnetic field simulations (CST MICROWAVE STUDIOÂź) were used to verify the uniform, in-plane magnetic field distribution (Bac) inside the sample area and optimize structure dimensions.
  3. Diamond Integration: A (111)-oriented Type Ib diamond substrate (2.5 x 2.5 x 0.5 mmÂł) was mounted on a copper socket centered within the ring cavity.
  4. Polarization Control: Microwave signals were split and routed through a programmable phase shifter (Δφ control) to two input ports, allowing continuous and arbitrary manipulation of the MW magnetic field polarization plane relative to the NV quantization axis.
  5. Frequency Tuning Implementation: Fixed 1.1 pF chip capacitors were replaced with commercial varactor diodes (SMV1232). By controlling the DC reverse bias voltage (1.5 V to 15 V), the device capacitance was varied, successfully shifting the resonant frequency (fres) across the 2.0-3.2 GHz range.
  6. ODMR Measurement: Continuous wave (CW) and pulsed ODMR techniques were employed. NV centers were initialized/readout using a 515 nm green laser, and resulting fluorescence was monitored by an Avalanche Photodiode (APD) to determine excitation purity and Rabi oscillation frequencies (fR).

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD is uniquely positioned to supply the advanced MPCVD diamond substrates and engineering support required to replicate or extend the capabilities demonstrated in this high-impact quantum research.

The project relies heavily on the specific crystal orientation and precise dimensions of the diamond substrate for successful orthogonal field alignment (Bdc || [111], Bac $\perp$ Bdc). 6CCVD ensures the availability of materials meeting these stringent criteria.

Research Requirement/Application6CCVD Applicable Materials6CCVD Engineering Advantage
High-Fidelity Quantum Control & MetrologyOptical Grade SCD (Single Crystal Diamond)Our SCD features extremely low nitrogen concentration necessary for maximizing NV center coherence times (T2). We guarantee the precise (111) orientation essential for maximizing NV spin alignment.
Custom Substrate DimensionsCustom-Sized Plates/WafersThe tested sample (2.5 x 2.5 x 0.5 mmÂł) falls perfectly within our custom cutting capability. We provide precise laser cutting services for plates/wafers up to 125 mm, ensuring exact integration geometry.
Precise Thickness ControlSCD Substrates up to 500 ”m ThicknessWe offer precise thickness control down to 0.1 ”m. The 0.5 mm thickness used here is a standard offering, ensuring reproducibility across large research studies.
Integrated Microwave Circuitry (RF/MW)Advanced Metalization ServicesAlthough this paper used external copper circuitry, future device miniaturization or BDD integration requires on-diamond metal contacts. 6CCVD provides in-house deposition of standard RF/MW metals (Au, Pt, Pd, Ti, W, Cu) for low-loss connectivity.
Optical Access (ODMR)Ultra-Smooth SCD PolishingFor high-efficiency optical detection (ODMR), surface quality is paramount. Our SCD substrates are polished to Ra < 1 nm, minimizing scattering losses and maximizing photon collection efficiency.
Broad Scope Magnetic ResonanceCustom BDD Diamond DopingFor experiments requiring conductive substrates or electrochemical sensing, we offer customized Boron-Doped Diamond (BDD) materials, available in both SCD and PCD forms, tailored to specific conductivity requirements.

Engineering Support: 6CCVD’s in-house PhD team can assist researchers with material selection, orientation verification, and geometric design considerations necessary for replicating or extending NV center quantum information and metrology projects.

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

View Original Abstract

We report on a planar microwave resonator providing arbitrarily polarized oscillating magnetic fields that enable selective excitation of the electronic spins of nitrogen-vacancy centers in diamond. The polarization plane is parallel to the surface of diamond, which makes the resonator fully compatible with (111)-oriented diamond. The field distribution is spatially uniform in a circular area with a diameter of 4 mm, and a near-perfect circular polarization is achieved. We also demonstrate that the original resonance frequency of 2.8 GHz can be varied in the range of 2-3.2 GHz by introducing varactor diodes that serve as variable capacitors.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1990 - Principles of Magnetic Resonance
  2. 2001 - Principles of Pulse Electron Paramagnetic Resonance

Reads Similar to This

Fast time response detectors of alpha particles fabricated using CVD diamonds Dual-frequency spin-resonance spectroscopy of diamond nitrogen-vacancy centers in zero magnetic field Cationic Surfactant Enhanced Detection of Tetrabromobisphenol A with Boron-doped Diamond Electrode