Double quantum magnetometry at large static magnetic fields
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-03-11 |
| Journal | Physical review. B./Physical review. B |
| Authors | Carlos Munuera-Javaloy, Íñigo Arrazola, E. Solano, J. Casanova |
| Institutions | Shanghai University, University of the Basque Country |
| Citations | 7 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research introduces a robust Double Quantum Magnetometry (DQM) protocol utilizing Nitrogen Vacancy (NV) centers in diamond, specifically designed for operation under large static magnetic fields (Bz).
- Enhanced Spectral Resolution: The DQM protocol inherently eliminates inhomogeneous broadening caused by magnetic field gradients, a critical limitation in standard Single Quantum Magnetometry (SQM), allowing for clear detection of natural frequency deviations like chemical shifts.
- Maximized Coupling Strength: A novel two-tone stroboscopic MW radiation pattern, featuring a “tailored Rabi frequency” (Ω(t)), is introduced to recover the ideal NV-nuclei coupling strength (fl), even when using realistic, long-duration pulses.
- Moderate Power Requirement: The tailored Ω(t) allows the use of moderate microwave (MW) power (maximum Rabi frequency of (2π) x 40 MHz), making the scheme practical for experimental implementation.
- High-Field Operation: The method is optimized for large static magnetic fields (e.g., 3 T), a regime where sensitive structural parameters, such as the chemical shift, are significantly enhanced.
- Robustness: The protocol demonstrates high tolerance to experimental imperfections, including 1% errors in MW field drivings and energy shifts up to (2π) x 20 kHz on the NV spin transitions.
- General Applicability: While demonstrated on NV centers, the protocol is general and adaptable to other quantum sensors (e.g., silicon vacancy centers) and various stroboscopic Dynamical Decoupling (DD) sequences.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sensor Type | Nitrogen Vacancy (NV) Center | N/A | Spin-1 quantum sensor in diamond lattice. |
| Target Static Magnetic Field (Bz) | 3 | T | Regime for enhanced chemical shift detection. |
| NV Zero Field Splitting (D) | (2π) x 2.87 | GHz | Intrinsic NV property. |
| NV Electron Gyromagnetic Ratio (γe) | (2π) x 28.024 | GHz/T | Used for MW frequency tuning. |
| 1H Larmor Frequency (ωL) | (2π) x 127 | MHz | At Bz = 3 T. |
| Tailored Rabi Frequency (Ωmax) | (2π) x 40 | MHz | Maximum required MW power (moderate). |
| Tailored Pulse Duration (tπ) | ≈ 0.16 | µs | Extended pulse length maintaining ideal coupling. |
| Non-Ideal Top-Hat Pulse Duration (tπ) | ≈ 7 | ns | Required for instantaneous pulses (high power). |
| Sequence Repetitions (N) | 360, 540 | N/A | Used for signal acquisition comparison. |
| MW Field Error Tolerance | 1 | % | Robustness against control field imperfections. |
| NV Transition Energy Shift Tolerance | (2π) x 20 | kHz | Robustness against NV spin transition errors. |
Key Methodologies
Section titled “Key Methodologies”The DQM protocol relies on precise control of the NV spin-1 manifold using engineered microwave pulses within a stroboscopic dynamical decoupling framework.
- DQM Spin Manifold Selection: The protocol operates on the S=1 manifold of the NV center, inducing rotations between the |1> and |-1> states via the |0> state using two-tone MW driving tuned to D ± |γe| Bz.
- Stroboscopic DD Sequence: The method utilizes three-pulse sequences (e.g., U[+1,-1,+1][π,0] and U[-1,+1,-1][π,π/2]) which, when repeated, effectively act as an Sz operator flip, forming the basis of the DD sequence (similar to XY family).
- Rabi Frequency Engineering: A specific, time-modulated Rabi frequency Ω(t) is calculated and applied to generate extended π-pulses. This modulation cancels out the destructive integral terms that typically reduce the coupling coefficient (fl) when using finite-width pulses.
- Resonance Condition: Enhanced NV-nuclei coupling is achieved when the sequence harmonic frequency (lωp) is matched to the nuclear Larmor frequency (ωL), allowing for resonant energy transfer.
- Inhomogeneous Broadening Mitigation: By utilizing the DQM scheme, the magnetic field gradient term (1/2 Σj A*j Ij) that causes spectral broadening in SQM is avoided, ensuring that observed spectral deviations are due to intrinsic sample properties (like chemical shift).
- Numerical Validation: The protocol’s performance, including the recovery of the ideal coupling coefficient and robustness against errors, was confirmed through numerical simulations of a 5-H spin cluster at 3 T.
Commercial Applications
Section titled “Commercial Applications”The robust, high-resolution magnetometry achieved by this DQM protocol is highly relevant for advanced sensing and materials science applications.
- Nanoscale NMR and MRI: Enables high-sensitivity, high-resolution Nuclear Magnetic Resonance (NMR) of extremely small samples (picoliters) or single molecules, crucial for chemical and structural analysis where sample volume is limited.
- Chemical Shift Spectroscopy: Optimized for operation at high static magnetic fields, facilitating the enhanced detection and characterization of chemical shifts, which encode vital structural information about chemical bonds.
- Quantum Sensing Platforms: Provides a robust, error-resistant control scheme for solid-state quantum sensors (like NV centers and silicon vacancy centers), improving their reliability in real-world environments with moderate control power limitations.
- Materials Science Characterization: Used for mapping and analyzing local magnetic environments and spin dynamics in novel materials, particularly those relevant to spintronics and quantum information science.
- Quantum Memory Development: The techniques for achieving strong, controlled coupling between the NV sensor and target nuclear spins are foundational for implementing quantum memories and hybrid quantum systems.
View Original Abstract
We present a protocol to achieve double quantum magnetometry at large static magnetic fields. This is a regime where sensitive sample parameters, such as the chemical shift, get enhanced facilitating their characterization. In particular, our method delivers two-tone stroboscopic radiation patterns with modulated Rabi frequencies to achieve larger spectral signals. Furthermore, it does not introduce inhomogeneous broadening in the sample spectrum preventing signal misinterpretation. Moreover, our protocol is designed to work under realistic conditions such as the presence of moderate microwave power and errors on the radiation fields. Albeit we particularise to nitrogen vacancy centers, our protocol is general, thus applicable to distinct quantum sensors.