Electrical control of coherent spin rotation of a single-spin qubit
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-09-08 |
| Journal | npj Quantum Information |
| Authors | Xiaoche Wang, Yuxuan Xiao, Chuan-Pu Liu, Eric Lee-Wong, Nathan J McLaughlin |
| Institutions | Colorado State University, University of California, San Diego |
| Citations | 28 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a critical breakthrough in achieving scalable and energy-efficient control of single-spin qubits by integrating Nitrogen-Vacancy (NV) centers with magnetic insulator nanostructures.
- Core Achievement: Electrical control of the coherent spin rotation rate (Rabi frequency, fRabi) of a single NV qubit using spin-orbit torque (SOT) generated in an adjacent Platinum (Pt) layer.
- Mechanism: SOT efficiently tunes the magnetic damping of the Yttrium Iron Garnet (YIG) strip, which in turn controls the amplitude of the oscillating stray magnetic field generated during Ferromagnetic Resonance (FMR).
- Efficiency and Amplification: The FMR condition amplified the effective microwave magnetic field experienced by the NV spin, resulting in a 10-fold enhancement of fRabi (from 0.8 MHz off-resonance to 9 MHz on-resonance).
- Electrical Tuning: The SOT mechanism provided efficient electrical tuning, demonstrating a systematic variation of approximately ±23% in the normalized fRabi/sqrt(P) when applying a current density of ±1 x 1011 A/m2.
- Propagating Spin Waves: Utilizing propagating spin wave modes yielded even higher amplification ratios, reaching up to 138 times for specific wavevectors (k2 mode).
- Scalability Potential: This hybrid solid-state approach offers a new, scalable, and energy-efficient method for local NV spin addressing, overcoming the limitations of conventional microwave striplines.
- Coherence Preservation: The measured spin coherent time is preserved, comparable to NV spins in bulk diamond, confirming the suitability of this hybrid platform for quantum operations.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| YIG Film Thickness (Strip Device) | 20 | nm | YIG/Pt strip for FMR experiments |
| YIG Film Thickness (Waveguide Device) | 100 | nm | YIG/Pt waveguide for propagating spin waves |
| Pt Film Thickness | 10 | nm | Layer generating spin-orbit torque (SOT) |
| NV Rabi Frequency (Off-Resonance) | 0.8 | MHz | Baseline measurement |
| NV Rabi Frequency (FMR Resonance) | 9 | MHz | Enhanced rate using quasi-uniform FMR mode |
| FMR Enhancement Ratio | ~11.25 | X | Ratio of resonant to off-resonant fRabi |
| Propagating SW Enhancement (k2 mode) | 138 | X | Highest observed amplification ratio |
| Electrical Tuning Range (fRabi/sqrt(P)) | ±23 | % | Variation achieved at maximum applied Jc |
| Applied Current Density (Jc) | ±1 x 1011 | A/m2 | Current used for SOT control |
| YIG Saturation Magnetization (Ms) | 1.31 x 105 | A/m | 20 nm YIG film parameter |
| Pt Spin Hall Angle (ΞSH) | 0.07 | - | Parameter used in SOT model |
| YIG Intrinsic Damping (α) | 0.001 | - | Parameter used in SOT model |
| Diamond Nanobeam Dimensions | 500 nm x 500 nm x 10 ”m | - | Approximate size of transferred NV structure |
Key Methodologies
Section titled âKey Methodologiesâ- Material Deposition: Y3Fe5O12 (YIG) films (20 nm and 100 nm) were deposited on (111)-oriented Gd3Ga5O12 (GGG) substrates using magnetron sputtering or liquid-phase epitaxy (LPE).
- Device Patterning (YIG/Pt Strip): Standard photolithography and ion mill etching were used to define 10 ”m wide, 50 ”m long YIG (20 nm)/Pt (10 nm) strips. A 500 nm thick Au stripline was fabricated proximally for microwave delivery.
- Device Patterning (CPW Waveguide): 80 ”m wide, 300 ”m long YIG (100 nm)/Pt (10 nm) waveguides were created, followed by the fabrication of perpendicular Au Coplanar Waveguides (CPWs) separated by a SiOx spacer.
- NV Nanobeam Fabrication and Transfer: Diamond nanobeams containing individual NV centers were fabricated using top-down etching and angle-etching, then transferred onto the magnetic nanostructures using a tungsten tip under a micromechanical stage to ensure nanoscale proximity.
- Optical and Magnetic Measurement: Experiments utilized a home-built scanning confocal microscope for optically detected magnetic resonance (ODMR) and NV Rabi oscillation measurements. A green laser initialized the NV spin state (ms = 0).
- Synchronized Electrical Control: Electric current pulses were applied to the Pt layer, synchronized with the microwave pulse, using an arbitrary waveform generator (AWG) to minimize current-induced Joule heating during the SOT application.
- Rabi Oscillation Measurement: The time duration of the microwave (and synchronized electrical) pulses was systematically varied to detect the time-dependent variation of the NV photoluminescence (PL) intensity, characterizing the coherent spin rotation rate (fRabi).
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Information Processing: Provides a pathway for developing scalable, high-density quantum registers based on solid-state NV qubits by enabling localized, energy-efficient spin control.
- Quantum Networks and Communications: The strong dipole coupling demonstrated between single NV spins and propagating magnons serves as an ideal medium for establishing long-range entanglement between distant NV spin qubits.
- High-Sensitivity Magnetometry: The ability to significantly enhance the NV Rabi frequency allows for faster quantum sensing protocols, improving the sensitivity and speed of magnetic field sensors.
- Hybrid Quantum-Spintronic Devices: Development of novel functional solid-state devices that integrate quantum emitters (NV centers) with magnonic circuits (YIG waveguides) for advanced signal processing and quantum transduction.
- Energy-Efficient Quantum Hardware: The use of SOT for control minimizes the high microwave current densities and associated Joule heating typically required for NV spin manipulation, leading to more energy-efficient quantum hardware.