Coherent microwave control of a nuclear spin ensemble at room temperature
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-04-15 |
| Journal | Physical review. B./Physical review. B |
| Authors | Paul Huillery, J. Leibold, Tom Delord, Nicolas Loménie, Jocelyn Achard |
| Institutions | Centre National de la Recherche Scientifique, Ăcole Normale SupĂ©rieure - PSL |
| Citations | 16 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a robust, room-temperature method for coherently controlling 14N nuclear spin ensembles within Nitrogen-Vacancy (NV) centers in diamond, utilizing nominally forbidden microwave transitions.
- Core Innovation: Coherent manipulation is achieved by applying a small, off-axis DC magnetic field (B â 0.01 T). This field tilts the electronic spin quantization axis, enabling efficient Electron-Nuclear Spin Transitions (ENST) in the microwave regime.
- High Coherence: Fast Rabi oscillations were observed on the ENST, with a frequency of 2Ï Ă 147 kHz and a damping time (TR) of 22 ”s, demonstrating high-quality coherent control of the nuclear ensemble.
- Quantum Memory Potential: The technique enabled Coherent Population Trapping (CPT) of the nuclear spin ensemble, yielding a narrow linewidth (8.2 kHz) and exceptionally high contrast (95%) at room temperature.
- New Polarization Method: A novel method was demonstrated to selectively polarize all three 14N nuclear spin states, achieving a polarization degree of approximately 60% without requiring the magnetic field to be aligned with the NV axis.
- Scalability: Coupling many NV electronic spins to their intrinsic 14N nuclei offers full scalability for quantum memories, potentially enabling a âN scaling of single photon coupling efficiency.
- Transduction Prospects: The results open clear pathways for long-lived storage of microwave photons (using EIT/CPT) and for coupling nuclear spins to mechanical oscillators (spin-mechanics) in the resolved sideband regime.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Host | 12C enriched bulk diamond | N/A | Grown by Chemical Vapor Deposition (CVD). |
| NV Center Concentration | â 0.3 | ppb | Concentration achieved via N2 injection during growth. |
| Operating Temperature | Room Temperature | °C | All coherent control experiments performed at ambient conditions. |
| Applied DC Magnetic Field (B) | â 0.01 (75 to 82.71) | T (G) | Off-axis configuration (angle Ξ â 87.8° to 89.7°). |
| Electron Spin Zero Field Splitting (D) | 2.87 | GHz | S=1 electron spin. |
| 14N Nuclear Zero Field Splitting (Q) | -4.945 | MHz | I=1 nuclear spin. |
| ENST Rabi Frequency (Ωa+) | 2Ï Ă 147(1) | kHz | Coherent driving of the nuclear spin ensemble. |
| Rabi Damping Time (TR) | 22(4) | ”s | Coherence time for the nuclear spin exchanging transition. |
| CPT Peak Width (FWHM) | 2Ï Ă 8.2(1.0) | kHz | Measured under specific optical/MW conditions. |
| CPT Contrast | 95(9) | % | Indicates high suppression of excited state population. |
| Achieved Nuclear Polarization | â 60 | % | Polarization degree for all three 14N nuclear spin states. |
| Optical Excitation Wavelength | 532 | nm | Green laser used for electron spin polarization. |
| Optical Excitation Power | 1 | mW | Focused by NA = 0.75 objective. |
| Electron Spin Polarization Rate (Îłlas) | 18 to 33.7 | kHz | Tunable via green laser power. |
Key Methodologies
Section titled âKey MethodologiesâThe experiments utilized an ensemble of NV centers in high-quality, 12C enriched bulk diamond grown via CVD, measured using Optically Detected Magnetic Resonance (ODMR) under a confocal microscope setup.
- Material Preparation: Bulk diamond was enriched with 12C to minimize environmental spin noise and grown via CVD with controlled N2 injection to achieve an NV concentration of approximately 0.3 ppb.
- Magnetic Field Application: A permanent magnet was positioned to apply a uniform, off-axis DC magnetic field (B â 75-83 G) at a large angle (Ξ â 88°) relative to the NV axis. The field magnitude and orientation were calibrated via reverse engineering of the electron spin ODMR spectra.
- Optical Setup: A 532 nm green laser (1 mW) was used for electron spin polarization and was controlled by an Acousto-Optic Modulator (AOM). Photoluminescence (PL) was collected, filtered (dichroic mirror, 532 nm notch filter), and detected by a Single-Photon Avalanche Photo-Detector (APD).
- Microwave (MW) Control: MW signals (single or two-tone) were generated using RF generators (Rohde & Schwarz SMB100A, DS Instruments SG4400L), combined, amplified, and fed to a single-loop antenna placed near the sample.
- Coherent Control Sequence:
- Preparation: Electron spins were polarized to the ms = 0 state using the green laser.
- Manipulation: MW pulses were applied to drive the Electron-Nuclear Spin Transitions (ENST).
- Readout: The resulting population was measured via the change in PL intensity (ODMR).
- Nuclear Polarization Sequence: A three-step sequence was used: Electron polarization (laser) -> MW pump (Ωp) tuned to an ENST -> Electron re-polarization (laser) -> Readout (MW pulse Ωr + PL measurement) to determine population in different nuclear states.
Commercial Applications
Section titled âCommercial ApplicationsâThe ability to coherently control long-lived nuclear spin ensembles at room temperature using microwave fields provides critical enabling technology for several advanced quantum applications.
| Application Area | Specific Use Case | Technical Advantage Provided by ENST |
|---|---|---|
| Quantum Computing/Memory | Microwave Photon Storage (EIT/CPT) | Enables the use of Electromagnetically-Induced Transparency (EIT) protocols for storing microwave photons in the long-lived 14N nuclear spin ensemble at room temperature. |
| Quantum Transduction | Spin-Mechanics Cooling | Facilitates reaching the resolved sideband regime (Ωm/2Ï > electron spin decay rate) necessary for cooling mechanical oscillators (e.g., levitating diamonds) to their motional ground state using nuclear spins. |
| Scalable Qubit Registers | Deterministic Qubit Initialization | Utilizes the intrinsic, deterministically present 14N nucleus as a robust qubit, offering uniform scaling and enhanced single-photon coupling efficiency (âN scaling). |
| Quantum Sensing (Metrology) | Long-Lived Spin Probes | Provides a method to initialize and coherently control highly isolated nuclear spins, which feature very low decay rates, enhancing the sensitivity and coherence time of quantum sensors. |
| Solid-State Qubit Control | Room-Temperature Qubit Gates | Offers a fast, controllable coupling scheme between the electron spin and the nuclear spin using AC microwave fields, crucial for implementing quantum gates without relying on complex cryogenic setups or high DC fields. |
View Original Abstract
We use nominally forbidden electron-nuclear spin transitions in\nnitrogen-vacancy (NV) centers in diamond to demonstrate coherent manipulation\nof a nuclear spin ensemble using microwave fields at room temperature. We show\nthat employing an off-axis magnetic field with a modest amplitude($\approx$\n0.01 T) at an angle with respect to the NV natural quantization axes is enough\nto tilt the direction of the electronic spins, and enable efficient spin\nexchange with the nitrogen nuclei of the NV center. We could then demonstrate\nfast Rabi oscillations on electron-nuclear spin exchanging transitions,\ncoherent population trapping and polarization of nuclear spin ensembles in the\nmicrowave regime. Coupling many electronic spins of NV centers to their\nintrinsic nuclei offers full scalability with respect to the number of\ncontrollable spins and provides prospects for transduction. In particular, the\ntechnique could be applied to long-lived storage of microwave photons and to\nthe coupling of nuclear spins to mechanical oscillators in the resolved\nsideband regime.\n