Solid-state electron spin lifetime limited by phononic vacuum modes
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-02-09 |
| Journal | Nature Materials |
| Authors | T. Astner, J. Gugler, A Angerer, S Wald, S. PĂŒtz |
| Institutions | Wolfgang Pauli Institute, University of Tsukuba |
| Citations | 59 |
| Analysis | Full AI Review Included |
Diamond Spin Qubit Relaxation: Technical Analysis and 6CCVD Solutions
Section titled âDiamond Spin Qubit Relaxation: Technical Analysis and 6CCVD SolutionsâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes research detailing the fundamental limits of electron spin relaxation in diamond Nitrogen Vacancy (NV-) centers, a critical platform for solid-state quantum computing and sensing.
- Quantum Limit Observation: Demonstrated the observation of the quantum limit for longitudinal spin relaxation ($T_1$) in NV- centers, where decay is governed by the spontaneous emission of phonons into the phononic vacuum.
- Record Spin Lifetimes: Achieved exceptionally long $T_1$ times of up to 8 hours (28,800 seconds) at ultra-low temperatures (T $\approx$ 25 mK).
- Mechanism Confirmation: Diamondâs high thermal conductivity effectively eliminates the phonon-bottleneck effect, confirming spontaneous phonon emission as the dominant relaxation mechanism at the quantum limit.
- Methodology: Employed a Cavity Quantum Electrodynamics (cQED) protocol using a 3D superconducting aluminum resonator ($Q = 60000$) dispersively coupled to a large ensemble of NV- spins.
- Material Dependence: The lowest measured spontaneous relaxation rate ($\Gamma_0 \approx 3.14 \times 10^{-5}$ s-1) was shown to depend strongly on lattice damage induced by irradiation (electron vs. neutron), but was independent of NV- density, indicating the coupling is intrinsic to the single NV center.
- Future Engineering: Results confirm the necessity of utilizing high-purity, low-defect diamond substrates for engineering highly coherent spin qubits, potentially utilizing phononic meta-materials to further tailor the density of states.
Technical Specifications
Section titled âTechnical SpecificationsâHard data extracted from the research paper detailing experimental parameters and results.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max Longitudinal Relaxation Time ($T_1$) | 8 | h | Achieved at T $\lt$ 50 mK (Quantum Limit) |
| Zero-Field Splitting ($\omega_s/2\pi$) | 2.88 | GHz | NV- ground state spin transition frequency |
| Spontaneous Relaxation Rate ($\Gamma_0$) (Lowest Measured) | $3.14 \times 10^{-5}$ | s-1 | Electron irradiated sample (E1), limits $T_1$ |
| Theoretical Ab Initio $\Gamma_0$ | $3.02 \times 10^{-5}$ | s-1 | Calculated rate, matching electron-irradiated samples |
| Resonator Fundamental Frequency ($\omega_0/2\pi$) | 3.04 | GHz | Superconducting 3D aluminum lumped element cavity |
| Resonator Quality Factor (Q) | 60000 | Dimensionless | Used for dispersive readout |
| Base Experimental Temperature | $\approx$ 25 | mK | Achieved via Adiabatic Demagnetization Refrigerator |
| NV- Concentration (N1 Sample) | 40 | ppm | Neutron irradiated, high lattice damage |
| NV- Concentration (E3 Sample) | 10 | ppm | Electron irradiated, lower lattice damage |
| Initial Nitrogen Concentration (N1/E3) | $\lt$ 200 | ppm | Type-Ib HPHT starting material |
| Annealing Temperature Range | 750-1000 | °C | Post-irradiation processing for NV formation |
Key Methodologies
Section titled âKey MethodologiesâA concise, step-by-step outline of the experimental procedure, focusing on material preparation and measurement conditions.
- Diamond Selection: Used Type-Ib High-Pressure High-Temperature (HPHT) diamond crystals from Element Six Ltd. with initial nitrogen concentrations typically $\lt$200 ppm.
- Vacancy Introduction:
- Samples were irradiated using either Neutron (0.1-2.5 MeV, dose up to $9.0 \times 10^{17}$ cm-2) or Electron (2 MeV to 6.5 MeV, dose up to $1.1 \times 10^{19}$ cm-2$) beams to create vacancies.
- NV Formation: Samples underwent high-temperature annealing (750 °C to 1000 °C) to facilitate vacancy migration and complexation with nitrogen to form the NV- center ensemble.
- Resonator Integration: Diamond samples were bonded using vacuum grease into a custom superconducting 3D lumped element cavity machined from EN AW 6066 aluminum (Ra $\approx 0.25$ ”m), tuned to $3.04$ GHz.
- Thermal Cycle Preparation: The spin ensemble was thermally initialized at a high temperature (2.7 K) where the spins were in thermal equilibrium with the environment.
- Relaxation Measurement: The system was non-adiabatically cooled to the target ultra-low temperature (25 mK to 400 mK). The time evolution of the ensembleâs magnetization ($S^{2}$) was continuously monitored via the state-dependent shift ($\chi$) of the cavity resonance frequency using a Vector Network Analyzer (VNA) at $-110$ dBm input power.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates that the ultimate performance of a diamond spin qubit relies on minimizing intrinsic lattice damage and optimizing crystal purity. 6CCVDâs advanced MPCVD technology and precision engineering services are perfectly suited to replicate and surpass the material quality required for this groundbreaking research.
Material Requirement Mapping
Section titled âMaterial Requirement Mappingâ| Research Requirement | 6CCVD MPCVD Diamond Solution | Technical Advantage & Sales Driver |
|---|---|---|
| Intrinsic High Purity (Minimize background defects) | Optical Grade Single Crystal Diamond (SCD) | Our MPCVD growth process achieves ultra-low native Nitrogen concentrations ($< 5$ ppb standard), dramatically reducing background paramagnetic defects that limit coherence and providing a superior, cleaner platform compared to the HPHT Type-Ib used. |
| Controlled Defect Engineering (Tailoring $\text{NV}^{\text{-}}$ ensemble) | Custom Doping, Irradiation, and Annealing Services | 6CCVD offers in-house control of both Boron Doping (BDD) and Nitrogen Doping during growth. We manage the subsequent high-temperature annealing and post-processing steps to achieve precise NV concentrations (e.g., 10-40 ppm) and optimize the NV charge state for spin qubit implementation. |
| High-Precision Surface Quality (Critical for cQED coupling) | Near-Atomic Surface Polishing | We provide SCD wafers with ultra-low surface roughness (Ra < 1 nm) and PCD surfaces (Ra < 5 nm for inch-size). This smooth interface minimizes microwave losses and ensures optimal coupling efficiency between the NV centers and the superconducting resonator. |
| Microwave Circuit Integration (Superconducting Al cavity) | Custom Metalization Capabilities | To seamlessly integrate the diamond crystal into cQED architectures, 6CCVD performs internal deposition of thin-film metal contacts, including Ti, Pt, Au, Cu, W, and Pd, directly onto the polished diamond surface, enabling robust superconducting wiring and grounding layers. |
| Custom Wafer Geometry (Precision mounting) | Advanced Substrate Fabrication & Dicing | We supply large-area PCD wafers (up to 125 mm) and custom-thickness SCD substrates (0.1 ”m - 500 ”m). Our laser cutting and mechanical processing services ensure custom dimensions and precise placement, vital for maintaining tight coupling tolerances within 3D lumped element resonators. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and technical engineers specialize in defect engineering and surface optimization. We provide expert consultation to researchers dedicated to replicating the ultra-low relaxation rates observed in this paper, assisting with material selection and custom processing required for similar solid-state quantum computing and ultra-low temperature spin physics projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.