Broadband microwave detection using electron spins in a hybrid diamond-magnet sensor chip
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-01-30 |
| Journal | Nature Communications |
| Authors | Joris J. Carmiggelt, Iacopo Bertelli, Roland W. Mulder, A. Teepe, Mehrdad Elyasi |
| Institutions | Tohoku University, Delft University of Technology |
| Citations | 40 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research introduces a novel hybrid sensor platform combining Nitrogen-Vacancy (NV) centers in diamond with a thin-film magnet (Yttrium Iron Garnet, YIG) to achieve broadband microwave (MW) detection.
- Core Value Proposition: Enables gigahertz (GHz) microwave sensing at fixed, small magnetic bias fields, circumventing the need for large, Tesla-scale magnets typically required for high-frequency NV sensing.
- Mechanism: Non-linear spin-wave dynamics (magnons) in the YIG film act as a frequency mixer. A pump field (fp) locally converts the target signal frequency (fs) to the fixed NV Electron Spin Resonance (ESR) frequency (fNV).
- Broadband Detection: Demonstrated two protocols: four-spin-wave mixing (achieving ~1 GHz detection bandwidth) and difference-frequency generation (detecting signals multiple GHz above fNV).
- Coherent Control: The converted microwave fields are highly coherent, allowing for high-fidelity, off-resonant Rabi control of the NV sensor spins over a gigahertz bandwidth.
- Frequency Combs: Generated spin-wave frequency combs, resolving up to the 10th idler order, which offers potential for enhanced sensitivity in microwave metrology and resolving closely spaced signal frequencies.
- Tunability: The detection frequency is pump-tunable, allowing characterization of magnetic band structures despite multi-GHz detuning from the NV ESR frequency.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Center Density | 103/”m2 | ”m-2 | Near-surface ensemble NV spins |
| NV Depth | 10-20 | nm | Below diamond surface |
| YIG Film Thickness | 235 | nm | Grown via Liquid Phase Epitaxy (LPE) |
| Diamond-YIG Separation | ~2 | ”m | Limited by small particles/dust |
| NV Zero-Field Splitting (D) | 2.87 | GHz | Electronic ground state |
| Electron Gyromagnetic Ratio (Îł) | 28 | GHz/T | Used in NV spin Hamiltonian |
| Target MW Frequency Range | 1-100 | GHz | Regime addressed by this technology |
| Detection Bandwidth (4-wave mixing) | ~1 | GHz | Achieved at fixed magnetic bias field |
| Highest Idler Order Resolved (n) | 10 | N/A | Observed in spin-wave frequency comb |
| Hyperfine Splitting (15N) | 3 | MHz | Resolved in idler-driven ESR spectrum |
| Optical Excitation Wavelength | 515 | nm | Continuous-wave PL readout |
| Rabi Pulse Readout Time | 300-400 | ns | Duration of second laser pulse |
| Signal/Pump Power (Typical) | 14 | dBm | Used for generating higher-order idler modes |
Key Methodologies
Section titled âKey MethodologiesâThe experimental setup relies on precise fabrication and integration of the magnetic film and the quantum sensor, followed by two distinct microwave conversion protocols:
- Sensor Platform Construction: A 2 x 2 x 0.05 mm3 diamond membrane containing near-surface NV centers (10-20 nm deep) was placed onto a 235 nm thick Yttrium Iron Garnet (YIG) film, which was grown on a GGG substrate. The diamond-YIG separation distance was approximately 2 ”m.
- Microwave Excitation: A microstrip line was used to deliver two continuous-wave microwave fieldsâthe signal (fs) and the pump (fp)âto the YIG film, exciting spin waves (magnons).
- NV ESR Stabilization: An external magnetic bias field (BNV) was applied to fix the NV Electron Spin Resonance (ESR) frequency (fNV), typically aligning with the âon-axisâ NV family.
- Four-Spin-Wave Mixing (4WM) Protocol: The pump frequency fp was tuned such that the non-linear interaction (scattering of two pump magnons into a signal magnon and an idler magnon) generated an idler frequency (fi = 2fp - fs) that was resonant with fNV, enabling detection of the signal.
- Difference-Frequency Generation (DFG) Protocol: The signal (fs) and pump (fp) fields drove the magnetization, generating a longitudinal component oscillating at the difference frequency (fp - fs). Detection occurred when this difference frequency was resonant with fNV, enabling sensing of signals detuned by multiple GHz.
- Coherent Control Measurement: Off-resonant Rabi oscillations were performed by initializing the NV spin using a green laser pulse, driving the spin using a pulsed pump field combined with a continuous-wave signal field (generating a pulsed idler at fNV), and reading out the spin state via a second laser pulse.
- Readout: NV photoluminescence (PL) was measured using a confocal microscope under non-resonant optical excitation (515 nm) to detect the spin state changes induced by the converted microwave fields.
Commercial Applications
Section titled âCommercial ApplicationsâThe hybrid diamond-magnet sensor chip opens new avenues for high-frequency characterization and quantum technology integration:
- Quantum Sensing and Metrology:
- Development of compact, pump-tunable broadband microwave sensors for applications requiring small magnetic bias fields.
- High-precision microwave metrology utilizing spin-wave frequency combs for enhanced resolution of closely spaced signals.
- Materials Science and Characterization:
- Probing high-frequency magnetic spectra of novel materials (e.g., van-der-Waals magnets) and thin films.
- Imaging spatial magnetization dynamics generated by spin-wave mixing using scanning-NV magnetometry.
- Quantum Information Processing:
- Enabling universal off-resonant quantum control of solid-state spins via magnon-mediated Rabi oscillations.
- Integration into hybrid quantum systems combining magnons and spins for advanced quantum computing architectures.
- RF/Microwave Component Testing:
- Characterization of local microwave generators, such as spin-torque oscillators.
- Detection of free-space microwaves using integrated on-chip microwave-to-spin-wave transducers.
View Original Abstract
Abstract Quantum sensing has developed into a main branch of quantum science and technology. It aims at measuring physical quantities with high resolution, sensitivity, and dynamic range. Electron spins in diamond are powerful magnetic field sensors, but their sensitivity in the microwave regime is limited to a narrow band around their resonance frequency. Here, we realize broadband microwave detection using spins in diamond interfaced with a thin-film magnet. A pump field locally converts target microwave signals to the sensor-spin frequency via the non-linear spin-wave dynamics of the magnet. Two complementary conversion protocols enable sensing and high-fidelity spin control over a gigahertz bandwidth, allowing characterization of the spin-wave band at multiple gigahertz above the sensor-spin frequency. The pump-tunable, hybrid diamond-magnet sensor chip opens the way for spin-based gigahertz material characterizations at small magnetic bias fields.