Tunable gyromagnetic augmentation of nuclear spins in diamond
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-01-13 |
| Journal | Physical review. B./Physical review. B |
| Authors | R. M. Goldblatt, A. Martin, A. A. Wood |
| Institutions | The University of Melbourne |
| Citations | 4 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled āExecutive SummaryāThis research demonstrates a method for achieving rapid, tunable quantum control over long-lived nuclear spins in diamond, addressing a critical bottleneck in solid-state quantum technology.
- Core Achievement: Demonstrated fast quantum control of optically-dark P1 center 14N nuclear spins in diamond at room temperature.
- Mechanism: Control speed is dramatically increased (gyromagnetic augmentation) by exploiting the hyperfine coupling between the P1 electron spin (S=1/2) and the 14N nuclear spin (I=1).
- Tunability: The augmentation factor is highly dependent on the external magnetic field (B). Control is fastest in the low-field regime (B < 100 G), where spin mixing is maximized.
- Performance: Measured Rabi frequencies reached up to 1.82 MHz, enabling gate operations comparable in speed to those typically achieved with electron spins, while retaining the long coherence benefits of nuclear spins.
- Methodology: Ensemble Nitrogen-Vacancy (NV) centers were used as sensitive probes via Double Electron-Electron Resonance (DEER) spectroscopy to characterize and drive the surrounding P1 spin bath.
- Implications: This work establishes a viable pathway for using P1 nuclear spins as high-quality, long-lived qubits in quantum registers, overcoming the challenge of slow manipulation inherent to bare nuclear spins.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Operating Temperature | Room Temperature | Ā°C | All experimental measurements. |
| Diamond Substrate Type | 1b | (111)-cut | Sample used for NV ensemble measurements. |
| Nitrogen (P1) Concentration | 1 | ppm | Concentration of paramagnetic defects. |
| Carbon-13 (13C) Abundance | 1.1 | % | Natural abundance; dominates NV coherence time. |
| Maximum External Magnetic Field (B) | 100 | G | Maximum field used in DEER/Rabi experiments. |
| Optimal Control Field Regime | < 100 | G | Regime where gyromagnetic augmentation is maximized. |
| Maximum Rabi Frequency (Ī©max) | 1.82 | MHz | Observed for P1 nuclear spin transitions (at 20 G). |
| Maximum Rabi Oscillation Amplitude (S(0)max) | 0.012 | (Normalized) | Observed at 20 G. |
| P1 Electron Gyromagnetic Ratio (Ī³e/2Ļ) | -2.8 | MHz/G | Constant for the P1 electron spin. |
| Bare 14N Nuclear Gyromagnetic Ratio (Ī³N/2Ļ) | 307.7 | Hz/G | Constant for the bare 14N nuclear spin. |
| P1 Axial Hyperfine Coupling (A||/2Ļ) | 114 | MHz | Interaction constant. |
| P1 Transverse Hyperfine Coupling (Aā„/2Ļ) | 81.34 | MHz | Interaction constant (dominates at low field). |
Key Methodologies
Section titled āKey MethodologiesāThe experiment relies on probing the P1 spin bath using an ensemble of NV centers via advanced pulsed magnetic resonance techniques.
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Sample and Setup:
- A Type 1b diamond sample (1 ppm N, 1.1% 13C) was mounted on a precision rotation stage (electric motor spindle).
- External magnetic fields (B, up to 100 G) were generated by current-carrying coils aligned along the NV axis.
- Microwaves (MW) were used for NV control, and radiofrequency (rf) fields were used for P1 control, generated by crossed wires and an I/Q modulated vector signal generator.
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DEER Spectroscopy (P1 Characterization):
- Double Electron-Electron Resonance (DEER) spectroscopy was employed to map the frequency spectrum of the P1 spin bath.
- An NV spin-echo pulse sequence was used, with the free evolution time fixed at a 13C revival time (45-65 Āµs) to maintain signal visibility.
- A resonant rf Ļ-pulse was swept in frequency during the spin-echo sequence to recouple specific P1 transitions to the NV centers, revealing both electron and nuclear spin transitions.
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Nuclear Rabi Oscillation Measurement:
- The P1 nuclear spin Rabi frequency (Ī©) was measured as a function of external magnetic field (B) strength.
- The length of the resonant rf pulse was varied, inducing Rabi oscillations in the P1 nuclear spin state, which were detected via the NV spin-echo signal contrast.
- Two specific nuclear spin transitions (ab and de) were targeted due to their isolation across the tested magnetic field range.
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Augmentation Factor Analysis:
- Rabi oscillation data was fitted to an exponentially-damped sinusoidal function to extract the Rabi frequency (Ī©) and amplitude (S(0)).
- The effective gyromagnetic ratio augmentation factor (Ī±) was calculated by normalizing the measured Rabi frequency (Ī©) against the bare nuclear gyromagnetic ratio (Ī³N) and the rf field amplitude (Brf), confirming the theoretical model based on hyperfine mixing.
Commercial Applications
Section titled āCommercial ApplicationsāThe ability to rapidly and tunably control long-lived nuclear spins in diamond has direct implications for several high-technology sectors:
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Quantum Computing and Memory:
- Qubit Implementation: Using P1 14N nuclear spins as robust, long-coherence qubits for quantum registers.
- Fast Gate Operations: Enabling rapid initialization and gate control, overcoming the typical speed limitations of nuclear spins.
- Dynamic Qubit Tuning: Creating hybrid qubits that can be switched dynamically between a fast-control regime (low B) and a long-storage regime (high B).
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Quantum Sensing and Metrology:
- Noise Mitigation: Utilizing fast P1 control to implement continuous dynamical decoupling schemes, suppressing P1-induced magnetic noise that limits NV coherence, thereby improving sensor sensitivity.
- High-Precision Gyroscopes: Developing diamond-based nuclear spin gyroscopes, leveraging the long coherence times and the demonstrated rapid, augmented control for enhanced readout speed.
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Solid-State Physics Research:
- Spin Bath Engineering: Providing a tool for detailed characterization and manipulation of dark spin baths in solid-state materials, crucial for understanding decoherence mechanisms in quantum systems.
View Original Abstract
Nuclear spins in solids exhibit long coherence times due to the small nuclear gyromagnetic ratio. This weak environmental coupling comes at the expense of slow quantum gate operations, which should be as fast as possible for many applications in quantum information processing and sensing. In this work, we use nitrogen-vacancy (NV) centers in diamond to probe the nuclear spins within dark paramagnetic nitrogen defects (P1 centers) in the diamond lattice. The gyromagnetic ratio of the P1 nuclear spin is augmented by hyperfine coupling to the electron spin, resulting in greatly enhanced coupling to radiofrequency control fields. We then demonstrate that this effect can be tuned by variation of an external magnetic field. Our work identifies regimes in which we are able to implement fast quantum control of dark nuclear spins, and lays the foundations for further inquiry into rapid control of long-lived spin qubits at room temperature.