Orbital and Spin Dynamics of Single Neutrally-Charged Nitrogen-Vacancy Centers in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-11-04 |
| Journal | Physical Review Letters |
| Authors | Simon Baier, C. E. Bradley, Thomas Middelburg, V. V. Dobrovitski, T. H. Taminiau |
| Institutions | QuTech, Delft University of Technology |
| Citations | 27 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: First direct spectroscopic observation and characterization of the orbital and spin dynamics of single neutrally-charged Nitrogen-Vacancy (NV0) centers in diamond.
- Fine Structure Revealed: Resonant excitation protocols successfully revealed the four transitions corresponding to the NV0 fine structure, validating theoretical models and enabling state-selective addressing.
- Orbital Dynamics: The orbital relaxation time (Torbit) was measured via pump-probe spectroscopy to be fast, 430 ns at 4.7 K, with temperature dependence suggesting two-phonon Orbach processes (characteristic energy Î â 12 meV).
- Spin Dynamics: The ground-state spin relaxation time (Tspin) was measured to be exceptionally long, 1.51 s, demonstrating the potential for NV0 as a robust quantum memory.
- High-Fidelity Control: A novel Charge-Resonance (CR) protocol was developed, enabling projective, high-fidelity single-shot readout of the NV0 spin state (Fidelity â„ 98.2%).
- System Parameters: Extracted Hamiltonian parameters include an orbital g-factor (l) of 0.039(11) and a spin-orbit interaction parameter (λ) of 4.9(4) GHz.
- Cyclicity: The optical cycling lifetime of the NV0 |â> state is limited by charge conversion, achieving a cyclicity of approximately 105 cycles at 5 nW excitation power.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Orbital Relaxation Time (Torbit) | 430(6) | ns | Measured at 4.65(3) K (Base Temperature) |
| Spin Relaxation Time (Tspin) | 1.51(1) | s | Ground state T1 relaxation time |
| Single-Shot Readout Fidelity (FRO) | â„ 98.2(9) | % | Lower bound achieved using a 5 photon threshold |
| Excited State Lifetime (Texc) | 22(1) | ns | Consistent with literature |
| Orbital g-factor (l) | 0.039(11) | - | Extracted from Hamiltonian fit |
| Spin-Orbit Interaction (λ) | 4.9(4) | GHz | Extracted from Hamiltonian fit |
| NV0 ZPL Wavelength (Yellow) | 575 | nm | Resonant excitation wavelength |
| NV- ZPL Wavelength (Red) | 637 | nm | Resonant excitation wavelength |
| Axial Magnetic Field (Bz) | 1890(5) | G | Applied to induce Zeeman splitting |
| Saturation Power (Psat) | 1.8(1) / 2.5(2) | nW | H / L polarization, NV0 ZPL |
| Spectral Diffusion Linewidth | 30.3(3) | MHz | Gaussian component, 4x transform limit |
| Charge Conversion Limited Cyclicity | 0.98(8) x 105 | cycles | For the |
| Orbach Process Energy Scale (Î) | 12(2) | meV | Associated with first vibronic level splitting |
Key Methodologies
Section titled âKey Methodologiesâ- Sample and Setup: Experiments performed on single NV centers in type-IIa bulk diamond (CVD grown, <111> oriented) using a 4 K cryogenic confocal microscope setup. Enhanced photon collection achieved via solid immersion lenses and anti-reflection coating.
- Magnetic Field Application: An axial magnetic field of Bz = 1890 G was applied using a permanent magnet to induce significant Zeeman splitting, enabling state-resolved addressing.
- Resonant Excitation: Both NV0 (Yellow, 575 nm ZPL) and NV- (Red, 637 nm ZPL) charge states were addressed using polarization-controlled resonant laser light. Microwave (mw) pulses were used for NV- ground-state spin transitions.
- Charge-Resonance (CR) Protocol: A novel heralded preparation sequence was implemented to ensure high-fidelity initialization into the NV0 state:
- Preparation: NV- state is prepared and checked using red light.
- Ionization: A strong red optical pulse induces NV- â NV0 conversion.
- Heralding: Yellow light resonant with a chosen NV0 transition confirms successful NV0 preparation above a photon count threshold.
- Spectroscopy and Parameter Extraction:
- Photoluminescence (PL) spectroscopy was performed using the CR protocol to observe the four NV0 fine structure transitions directly.
- Transition frequencies and polarization-dependent amplitudes were fitted against the theoretical Hamiltonian to extract the orbital g-factor (l) and spin-orbit parameter (λ).
- Orbital Dynamics Measurement (Pump-Probe): Time-resolved pump-probe spectroscopy was used to measure Torbit. A strong yellow pump pulse depopulates the driven orbital state, and a subsequent probe pulse measures the recovery timescale when illumination is turned off.
- Spin Dynamics Measurement (Tspin): The NV0 spin relaxation time was measured by preparing the |â> state, introducing a long dark delay (up to 10 s), and then reading out the resulting mixed spin populations.
- Master Equation Modeling: A Lindblad master equation model was developed and fitted to the time-resolved fluorescence data, incorporating measured timescales (Texc, Torbit, Tspin) and spectral properties to confirm a consistent understanding of NV0 dynamics.
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Information Processing (QIP): NV0 centers, with their long spin coherence (Tspin â 1.5 s), are promising candidates for solid-state quantum memory registers.
- Quantum Networks: The ability to control and characterize NV0 dynamics is crucial for mitigating decoherence caused by stochastic NV- â NV0 conversion, improving the reliability of nuclear-spin quantum memories.
- Quantum Sensing: Understanding the NV0 orbital structure and dynamics provides new insights into the local electric and strain environment, potentially enabling new modalities for quantum sensing applications.
- Spin-to-Charge Conversion: The NV0 state is an intermediate step in spin-to-charge conversion protocols, which are used to achieve high-fidelity, fast spin readout in NV- systems.
- Defect Engineering in Diamond: The detailed characterization of NV0 provides fundamental knowledge applicable to engineering other color centers and impurities in wide bandgap semiconductors for quantum technology.
View Original Abstract
The neutral charge state plays an important role in quantum information and sensing applications based on nitrogen-vacancy centers. However, the orbital and spin dynamics remain unexplored. Here, we use resonant excitation of single centers to directly reveal the fine structure, enabling selective addressing of spin-orbit states. Through pump-probe experiments, we find the orbital relaxation time (430 ns at 4.7 K) and measure its temperature dependence up to 11.8 K. Finally, we reveal the spin relaxation time (1.5 s) and realize projective high-fidelity single-shot readout of the spin state (â„98%).