Quantum nonlinear spectroscopy of single nuclear spins
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-09-09 |
| Journal | Nature Communications |
| Authors | Jonas Meinel, Vadim Vorobyov, Ping Wang, Boris Yavkin, Matthias Pfender |
| Institutions | University of Stuttgart, Max Planck Institute for Solid State Research |
| Citations | 21 |
| Analysis | Full AI Review Included |
Quantum Nonlinear Spectroscopy of Single Nuclear Spins: Material Solutions by 6CCVD
Section titled âQuantum Nonlinear Spectroscopy of Single Nuclear Spins: Material Solutions by 6CCVDâThis technical documentation analyzes the requirements for advanced quantum sensing experiments, specifically Quantum Nonlinear Spectroscopy (QNS) utilizing Nitrogen-Vacancy (NV) centers in diamond. 6CCVD provides the ultra-high purity, isotopically controlled Single Crystal Diamond (SCD) substrates necessary to replicate and advance this cutting-edge research.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstration of Quantum Nonlinear Spectroscopy (QNS) using an NV center in diamond to extract arbitrary, high-order correlations (specifically fourth-order) of single nuclear spins ($^{13}$C).
- Quantum Differentiation: QNS successfully provides âfingerprint featuresâ that unambiguously differentiate quantum spins from classical noise sources (Gaussian noise, random-phased AC fields), which are indistinguishable using conventional second-order correlations.
- Quantized Counting: The technique enables a discrete, quantized count of the number of coupled nuclear spins, analogous to $g^{(2)}$ measurements in quantum optics.
- Material Requirement: The experiment relies critically on ultra-high purity, isotopically enriched Single Crystal Diamond (SCD) (99.995% $^{12}$C) to maximize the NV center electron spin coherence time ($T_2 \approx 300$ ”s).
- Methodology: The protocol employs sequential weak measurement combined with robust Knill Dynamical Decoupling (KDD-XY5) sequences under a 0.2502 T magnetic field.
- Future Applications: This work is foundational for applying higher-order correlations to quantum sensing, testing quantum foundations (e.g., Leggett-Garg inequality), and studying quantum many-body physics.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper, detailing the physical and operational parameters critical for the QNS experiment.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Isotopic Purity | 99.995 | $^{12}$C Enrichment | Required for long coherence times ($T_2$) by minimizing spin bath noise. |
| Substrate Orientation | (111) | Crystal Plane | Used for NV center creation and alignment. |
| Substrate Dimensions | 2 x 2 x 0.08 | mm | 80 ”m thickness. |
| NV Center $T_2$ Lifetime | ~300 | ”s | Measured by spin echo; critical for high-resolution spectroscopy. |
| Magnetic Field ($B_0$) | 0.2502 | T | Applied parallel to the NV axis (z-direction). |
| NV Transition Frequency | ~4.1 | GHz | Microwave frequency for $ |
| Electron Spin Rabi Frequency | 7 | MHz | Used for high-fidelity spin manipulation. |
| Interrogation Time ($t_c$) | 470.4800 | ”s | Specific time used for $^{13}$C nuclear spin measurement. |
| Dynamical Decoupling | KDD-XY5, $N_p=100$ | N/A | Sequence used to modulate interaction and suppress environmental noise. |
| Interaction Strength ($\alpha$) | 0.189$\pi$ | Radians | Weak, tuneable entanglement strength induced during interrogation. |
Key Methodologies
Section titled âKey MethodologiesâThe QNS protocol relies on precise control over the NV center sensor and the high-purity diamond environment. The key steps of the sequential weak measurement are:
- Sample and Setup: A 99.995% $^{12}$C-enriched, (111)-oriented SCD slice (80 ”m thick) containing electron-irradiated NV centers is placed in a confocal microscope setup under a 0.2502 T superconducting magnetic field.
- Sensor Initialization: The NV electron spin is optically pumped (532 nm laser) to the $|0>$ state, then prepared into the $|x>$ superposition state using a microwave $\pi/2$-pulse.
- Interrogation and Entanglement: The sensor spin ($S_z$) is weakly coupled to the target $^{13}$C nuclear spin bath. This interaction is modulated by a Knill Dynamical Decoupling (KDD-XY5) sequence ($N_p=100$) to induce weak, tuneable entanglement.
- Weak Measurement: The sensor spin is rotated by a phase-shifted MW pulse and measured along a chosen basis ($\hat{\sigma}_\theta$, where $\theta \approx 54.0037^\circ$ maximizes the third-order signal).
- Readout Enhancement: To enhance fidelity, the sensor state is transferred to the long-lived $^{14}$N nuclear spin (quantum memory) via SWAP gates, allowing for repetitive readout (40 repetitions) using CNOT gates and spin-dependent fluorescence detection.
- Correlation Analysis: The statistical moments ($S_i, S_{ij}, S_{ijk}$) of the sequential measurement outputs ($\sigma_j = \pm 1$) are reconstructed from the photon counts to extract the classical and quantum contributions to the third and fourth-order correlations.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced diamond materials required for high-fidelity quantum nonlinear spectroscopy and related quantum sensing applications.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, the primary material requirement is ultra-low strain, isotopically pure diamond.
| Research Requirement | 6CCVD Material Solution | Technical Justification |
|---|---|---|
| Ultra-High Purity $^{12}$C | Optical Grade Single Crystal Diamond (SCD) | Essential for achieving long coherence times ($T_2 \approx 300$ ”s) by minimizing paramagnetic impurities and reducing the nuclear spin bath noise. |
| Specific Crystal Orientation | Custom (111) or (100) SCD Plates | We supply SCD wafers with precise crystallographic orientation, crucial for aligning the NV axis with the external magnetic field ($B_0$). |
| Thin, Polished Substrate | Custom Thickness SCD Wafers | The paper used an 80 ”m thick slice. 6CCVD offers SCD thickness control from 0.1 ”m up to 500 ”m, allowing optimization for NV creation depth and optical access. |
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs MPCVD growth and post-processing capabilities directly address the specific engineering needs of quantum sensing platforms:
- Custom Dimensions and Thickness: We can supply SCD plates in custom dimensions (e.g., 2 mm x 2 mm) and thicknesses (e.g., 80 ”m) with high precision, ensuring compatibility with specialized confocal microscope setups and superconducting magnets.
- Polishing Specifications: The experiment requires high-quality optical surfaces. 6CCVD guarantees ultra-low surface roughness: Ra < 1 nm for SCD substrates, minimizing scattering losses and improving optical coupling efficiency.
- Metalization Services: While this paper did not detail on-chip electrodes, future extensions of QNS (e.g., integrating microwave control lines or micro-magnets) require metalization. 6CCVD offers in-house deposition of standard metals including Au, Pt, Pd, Ti, W, and Cu for custom device fabrication.
- Isotopic Control: We specialize in providing high-purity $^{12}$C diamond (up to 99.999%) necessary for maximizing $T_2$ coherence, a prerequisite for high-resolution quantum spectroscopy.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers provides authoritative professional support for complex quantum projects. We assist researchers in selecting the optimal diamond specifications (orientation, isotopic purity, and surface preparation) to maximize NV center performance for similar Quantum Nonlinear Spectroscopy and high-resolution NMR projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.