Optical Control of a Single Nuclear Spin in the Solid State
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-04-15 |
| Journal | Physical Review Letters |
| Authors | Michael Goldman, Taylor L. Patti, David Levonian, Susanne F. Yelin, M. D. Lukin |
| Institutions | Harvard University, University of Connecticut |
| Citations | 22 |
| Analysis | Full AI Review Included |
Technical Documentation: All-Optical Coherent Nuclear Spin Control in Diamond NV Centers
Section titled âTechnical Documentation: All-Optical Coherent Nuclear Spin Control in Diamond NV Centersâ(Analysis of arXiv:1808.04346v1)
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a powerful, all-optical technique for coherent manipulation of individual nuclear spins ($\text{N}^{14}$) mediated by the electronic states of the Nitrogen-Vacancy (NV) color center in diamond. This methodology is critical for developing high-density, integrated solid-state quantum memory devices.
- Novel Methodology: Coherent control of a proximal 14N nuclear spin is achieved using an all-optical Raman technique leveraging the Excited State Level Anti-Crossing (ESLAC) of the NV electronic spin-triplet.
- Performance Metrics: Extracted hyperfine and quadrupole splittings (A/h = -2.151 MHz, P/h = -4.942 MHz) align closely with previous measurements, confirming precise spin state resolution.
- High Efficiency Polarization: The method achieves efficient nuclear spin polarization ($\approx 87%$) using tailored optical pumping transitions, distinct from nonresonant methods.
- Scalability for Qubit Arrays: All-optical approaches offer faster manipulation and significantly higher spatial resolution compared to traditional microwave (MW) or radio-frequency (RF) techniques, making them ideal for dense nanophotonic integration.
- Coherence Limitations: The coherence and speed of the optical control are fundamentally limited by the ratio of the transverse hyperfine coupling rate ($\lambda_{\perp}$) to the excited state radiative decay rate ($\gamma$), suggesting a need for materials optimization.
- Material Requirement: The demonstrated precision requires ultra-high purity, low-strain Single Crystal Diamond (SCD) substrates suitable for the creation and stable operation of isolated NV centers at cryogenic temperatures.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Host Material | Diamond | N/A | Nitrogen-Vacancy (NV) color center |
| Primary Raman Wavelength ($\lambda_{\text{Raman}}$) | 637 | nm | Used for two-photon detuning spectroscopy |
| Initialization Wavelength ($\lambda_{\text{Init}}$) | 520 | nm | Used for electronic spin initialization |
| Cryogenic Operating Temperature | ~7 | K | Coldfinger temperature for experimental runs |
| Extracted Sample Temperature (ISC) | 14 ± 1 | K | Derived from phonon-induced mixing rate |
| Axial Hyperfine Coupling ($A/h$) | -2.151(4) | MHz | Key parameter for 14N ground state structure |
| Quadrupole Shift ($P/h$) | -4.942(9) | MHz | Key parameter for 14N ground state structure |
| Nuclear Zeeman Shift ($\gamma_{N} B_{z}/h$) | -118 | kHz | Magnetic field applied along N-V axis |
| Electronic Spin Decoherence Limit | $\lambda_{\perp}/\gamma \approx 2$ | Ratio | Ratio of transverse hyperfine coupling to radiative decay |
| Measured Nuclear Polarization | $\approx 87$ | % | Achieved via selective optical pumping |
| Excited State Strain Splitting ($\delta$) | 5.5 | GHz | Extracted from PLE spectroscopy fit |
| Raman Detuning ($\Delta$) | $\approx 870$ | MHz | Below $ |
Key Methodologies
Section titled âKey MethodologiesâThe experiment successfully demonstrated initialization, coherent manipulation, and readout of a single 14N nuclear spin using the following steps:
- NV Center Initialization: The NV center was initialized to the negatively charged state using 520 nm green laser light.
- Electronic Spin Preparation: Optical pumping was applied to polarize the electronic spin into the orbital-singlet ground state ($|0\rangle$).
- Raman Driving Field Generation: Two optical driving fields, slightly detuned ($\Delta \approx 870$ MHz) from the excited state, were created by modulating a single 637 nm laser using an electro-optic modulator (EOM) to ensure relative phase stability and precise control over the frequency difference ($\delta_L$).
- Spectroscopy of Hyperfine Structure: By sweeping the two-photon detuning ($\delta_L$), the multiple hyperfine transitions between $|0\rangle$ and $|+1\rangle$ electronic states were mapped out, revealing both spin-conserving (blue lines) and electron-nuclear flip-flop (green lines) transitions.
- Nuclear Spin Polarization (Optical Pumping): A novel selective optical pumping method was employed, pumping simultaneously on the $|+1\rangle \rightarrow |E_1\rangle$ and $|0\rangle \rightarrow |E_2\rangle$ transitions. This process resulted in a net transfer of polarization to the nuclear spin, achieving $\approx 87%$ polarization into $m_I = +1$.
- Coherent Dynamics Measurement: Coherent oscillations (Rabi oscillations) were measured by varying the duration of the selective Raman pulse, confirming conditioned electronic spin control and optical transfer of nuclear population.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical reliance on high-quality, customized diamond materials for advancing solid-state quantum computing and memory. 6CCVD provides the necessary materials and engineering expertise to replicate, optimize, and scale these foundational experiments.
Applicable Materials
Section titled âApplicable MaterialsâThe precise control demonstrated hinges on minimizing external decoherence, requiring ultra-high purity, low-strain single crystal diamond (SCD) material optimized for quantum applications.
| Material Specification | Requirement for Replication | 6CCVD Offering | Advantage |
|---|---|---|---|
| SCD Substrates | Ultra-low strain, high crystal quality, low background nitrogen ($< 5$ ppb) for NV creation via implantation. | Optical Grade SCD (Purity Level 1). Thickness control: 0.1 ”m to 500 ”m | Superior spectral stability and reduced decoherence ($\Gamma_{\text{ISC}}$) for prolonged coherence times. |
| Isotopically Pure Diamond | Future extension of this work (as referenced) requires $^{12}$C enrichment to extend nuclear spin coherence ($\tau_c > 1s$). | SCD $\text{C}^{12}$ enriched wafers (available up to 10mm substrates). | Essential for maximizing coherence time ($\text{T}_2$) by removing residual $^{13}\text{C}$ coupled spins. |
| Boron-Doped Diamond | Alternate solid-state color centers (e.g., SiV) are discussed as extensions. BDD may be relevant for specific electrochemistry applications. | Boron-Doped Diamond (BDD) films (PCD or SCD) up to 500 ”m. | Provides flexibility for exploring other quantum emitters and integrated devices. |
Customization Potential
Section titled âCustomization PotentialâThe experimental focus on integration into nanophotonic devices and the need for magnetic field control necessitate custom engineering solutions.
- Custom Dimensions and Etching: 6CCVD offers single crystal wafers up to $\mathbf{125mm}$ (Polycrystalline) and standard SCD wafers, which can be custom laser cut or etched to produce samples tailored for cryostat mounting, microwave delivery structures, or nanophotonic integration templates.
- Precision Polishing: The study requires extremely low surface roughness to ensure high-fidelity optical interfaces, especially for integrated quantum arrays. 6CCVD guarantees $\mathbf{Ra < 1nm}$ polishing for SCD and $\mathbf{Ra < 5nm}$ for inch-sized PCD, ensuring minimal surface scattering losses for 637 nm excitation.
- Advanced Metalization: While the paper used external magnets, integration often requires on-chip electrodes. 6CCVD provides in-house metalization services, including Au, Pt, Pd, Ti, W, and Cu layers, crucial for creating integrated MW/RF delivery structures near the NV centers.
Engineering Support
Section titled âEngineering SupportâThe complexity of controlling the electronic-nuclear systemâparticularly the optimization of Rabi frequency ($\tilde{\Omega}{ab}$) relative to incoherent optical pumping ($\Gamma{ab}$)âdemands deep technical insight.
- Consultation on Material Purity: 6CCVDâs in-house PhD team provides specialized consultation to researchers replicating or extending this solid-state quantum control project, assisting with material specifications (e.g., nitrogen concentration, C12 enrichment level) to optimize $\lambda_{\perp}/\gamma$ for enhanced coherence.
- Decoherence Mitigation Strategies: We assist engineers in selecting appropriate materials and surface preparation techniques to mitigate critical decoherence factors identified in the study, such as phonon-induced mixing and intersystem crossing (ISC) rates.
- Global Logistics: We ensure reliable global delivery (DDU default, DDP available) of sensitive, high-value diamond materials essential for cryo-electronic research worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We demonstrate a novel method for coherent optical manipulation of individual nuclear spins in the solid state, mediated by the electronic states of a proximal quantum emitter. Specifically, using the nitrogen-vacancy (NV) color center in diamond, we demonstrate control of a proximal ^{14}N nuclear spin via an all-optical Raman technique. We evaluate the extent to which the intrinsic physical properties of the NV center limit the performance of coherent control, and we find that it is ultimately constrained by the relative rates of transverse hyperfine coupling and radiative decay in the NV centerâs excited state. Possible extensions and applications to other color centers are discussed.