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6CCVD Research

Sensing Coherent Dynamics of Electronic Spin Clusters in Solids

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2018-06-15
JournalPhysical Review Letters
AuthorsEmma Rosenfeld, Linh Pham, M. D. Lukin, Ronald L. Walsworth
InstitutionsHarvard University, Center for Astrophysics Harvard & Smithsonian
Citations22
AnalysisFull AI Review Included

Technical Analysis & Product Solution: Coherent Spin Dynamics in MPCVD Diamond

Section titled “Technical Analysis & Product Solution: Coherent Spin Dynamics in MPCVD Diamond”

This technical documentation analyzes the requirements and findings of the research paper, “Sensing coherent dynamics of electronic spin clusters in solids,” and translates them into actionable material recommendations and custom fabrication solutions available through 6CCVD.

Executive Summary

Section titled “Executive Summary”
  • Quantum Core Achievement: Direct observation of coherent spin exchange (flip-flop dynamics) between two identical, optically-dark S = 1/2 electron spins in a solid-state diamond substrate, mediated by a single Nitrogen Vacancy (NV) center.
  • Room Temperature Quantum Gates: The work establishes a vital prerequisite for realizing fast quantum gate operations and quantum state transfer in a scalable, room-temperature quantum processor architecture.
  • Material Foundation: Experimentation relied on high-purity, electronic grade, polycrystalline diamond featuring a 99.999% 12C layer to maximize coherence times and suppress nuclear spin noise.
  • Key Parameters Extracted: Detailed ODMR and SEDOR spectroscopy quantified the NV-electron coupling strengths ($A_1, A_2$) and the direct electron-electron coupling ($J_{12}$), validating a theoretical model of strongly interacting spins.
  • Coherence & Dynamics: Measured electron spin coherence time ($T_2^*$) of 14 ”s was observed, and coherent polarization transfer between the NV and the dark spin pair was demonstrated using the Hartmann-Hahn technique.
  • Fabrication Requirements: NV centers were created via low-energy (2.5 keV) 14N implantation, requiring precise surface control and subsequent 900 °C vacuum annealing.

Technical Specifications

Section titled “Technical Specifications”

The following key material and performance parameters were extracted from the study:

ParameterValueUnitContext
Substrate TypePolycrystallineElectronic GradeElement Six CVD-grown sample
Carbon Purity99.999%12CLayer grown on substrate
NV Implantation Energy2.5keV14N and 14N2 ions
Annealing Parameters900 °C / 8 hoursVacuumNV activation and stabilization
NV Depth (Estimated)5-10nmRequired for coupling to surface dark spins
NV-e- Coupling ($A_1$)0.81(5)MHzDipolar coupling constant
NV-e- Coupling ($A_2$)-0.86(5)MHzDipolar coupling constant
e--e- Coupling ($J_{12}$) (Half)±0.38(5)MHzElectron spin-spin coupling strength
Dark Spin Flip-Flop Rate ($\Delta_1$)0.41(5)MHzConditional on NV $m_s=0$ state
Electron Spin Coherence Time ($T_2^*$)14(3)”sMeasured via SEDOR exponential decay
Magnetic Bias Field ($B_0$)694.0GUsed for spectroscopy and splitting
MW Delivery Structure$\Omega$-shaped Stripline100 ”m IDUsed for 900 MHz (NV) and 2000 MHz (e-) drives

Key Methodologies

Section titled “Key Methodologies”

The experimental approach combines advanced MPCVD diamond substrate preparation with sophisticated quantum sensing techniques:

  1. Material Selection and Growth: Use of high-purity (99.999% 12C), electronic-grade polycrystalline diamond, grown along the {110} direction via Chemical Vapor Deposition (CVD). The initial surface was unpolished.
  2. NV Center Engineering: Creation of NV centers through low-energy (2.5 keV) ion implantation of 14N, followed by high-temperature (900 °C) annealing in vacuum for 8 hours to activate the defects.
  3. Experimental Setup: Utilization of a home-built 4f confocal microscope for optical NV initialization (532 nm laser) and photoluminescence readout, filtered and detected via a single photon counter.
  4. Microwave Control: High-frequency, dual-channel waveforms were synthesized using an arbitrary waveform generator, amplified, and delivered via an on-chip, 100 ”m inner diameter $\Omega$-shaped stripline, enabling precise NV and electron spin Rabi driving frequencies (900-2000 MHz).
  5. Quantum State Probing: Measurement of spin dynamics and coupling constants via optically detected magnetic resonance (ODMR), Dynamical Decoupling (DD), Spin Echo Double Resonance (SEDOR), and Double Electron-Electron Resonance (DEER) experiments.
  6. Coherent Manipulation: Demonstration of quantum state transfer via the Hartmann-Hahn cross-polarization technique by matching dressed state energies between the NV and the dark spin pair.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD is uniquely positioned to supply the advanced diamond materials and custom engineering services required to replicate, extend, or scale the quantum technologies demonstrated in this research.

Applicable Materials

Section titled “Applicable Materials”

To achieve high-fidelity spin coherence and enable scalable quantum registers, researchers should utilize 6CCVD’s specialized offerings:

  • Isotope-Enriched Single Crystal Diamond (SCD): To minimize background noise and maximize the intrinsic spin coherence time ($T_2$), we recommend ultra-high purity 12C SCD. While the paper utilized polycrystalline material, SCD offers superior defect control and lattice uniformity, resulting in $T_2$ times significantly exceeding the 14 ”s reported for the dark spins.
    • Specification: SCD wafers up to 10mm thickness, with 12C enrichment > 99.999%.
  • Electronic Grade PCD: For cost-sensitive, large-area applications or for replicating the exact conditions of the published work, 6CCVD provides Electronic Grade Polycrystalline Diamond (PCD) wafers up to 125mm in diameter.

Customization Potential

Section titled “Customization Potential”

The success of this experiment relies heavily on precise NV placement and efficient microwave delivery—areas where 6CCVD provides critical in-house engineering support.

Requirement from Paper6CCVD Custom SolutionRelevance to Quantum Research
Implantation/AnnealingPre-engineered substrates ready for NV formation, tailored for specific keV and dose requirements.Ensures reproducible NV concentration and depth (5-10 nm) near the surface for coupling to dark spins/dangling bonds.
MW Delivery StructureCustom Metalization (Au, Pt, Ti, Pd, W, Cu) patterning via lithography.Enables fabrication of high-fidelity $\Omega$-shaped striplines, CPW, or other custom microwave circuit elements directly onto the diamond surface for optimized field homogeneity and power delivery.
Surface FinishAtomic-Flat Polishing (Ra < 1 nm for SCD, Ra < 5 nm for PCD).While the paper used an unpolished sample, atomic-flat surfaces are critical for near-surface NV centers (5-10 nm deep) to mitigate decoherence caused by surface defects.
Custom DimensionsLaser-cut plates and wafers up to 125mm diameter.Provides ready-to-mount diamond chips cut precisely to fit existing quantum apparatus or cryostats, eliminating post-processing risks.

Engineering Support

Section titled “Engineering Support”

6CCVD’s in-house PhD team provides authoritative support, specializing in the complex material-physics interface required for advanced quantum applications. We can assist researchers with:

  • Material Selection: Guidance on optimizing carbon purity and defect engineering (e.g., nitrogen concentration control) to maximize the $T_2$ coherence time for new room-temperature quantum register projects.
  • Post-Processing Optimization: Consultation on annealing procedures and surface preparation techniques necessary for reproducible creation of high-quality, shallow NV centers compatible with coherent spin coupling.
  • Boron Doping (BDD): For applications requiring integrated quantum devices or sensing in liquid environments, 6CCVD offers custom Boron-Doped Diamond (BDD) materials, providing exceptional electrochemical and sensing properties.

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

View Original Abstract

We observe coherent spin exchange between identical electronic spins in the solid state, a key step towards full quantum control of electronic spin registers in room temperature solids. In a diamond substrate, a single nitrogen vacancy (NV) center coherently couples to two adjacent S=1/2 dark electron spins via the magnetic dipolar interaction. We quantify NV-electron and electron-electron couplings via detailed spectroscopy, with good agreement to a model of strongly interacting spins. The electron-electron coupling enables an observation of coherent flip-flop dynamics between electronic spins in the solid state, which occur conditionally on the state of the NV. Finally, as a demonstration of coherent control, we selectively couple and transfer polarization between the NV and the pair of electron spins. Our observations enable the realization of fast quantum gate operations and quantum state transfer in a scalable, room temperature, quantum processor.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2001 - Principles of Pulse Electron Paramagnetic Resonance [Crossref]

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