All-optical reconfiguration of single silicon-vacancy centers in diamond for non-volatile memories
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-07-08 |
| Journal | Nature Communications |
| Authors | Yongzhou Xue, Xiaojuan Ni, Michael Titze, Shei Sia Su, BoâHan Wu |
| Institutions | The University of Texas at Austin, University of Arizona |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research introduces a novel, all-optical method for non-volatile local strain engineering of single silicon-vacancy (SiV) centers in diamond, enabling high-performance quantum and classical memory applications.
- Core Mechanism: High-power picosecond pulsed laser irradiation triggers the migration of nearby lattice defects (vacancies/self-interstitials), leading to a permanent, non-volatile modification of the local crystal strain experienced by the SiV center.
- Performance Achievement: Demonstrated a significant enhancement of the SiV Ground State (GS) splitting, achieving up to 1.8 THz, which is critical for suppressing acoustic phonon interaction and improving spin coherence time.
- Non-Volatile Memory: The two distinct, stable strain states (s1 and s2) are utilized to encode binary data (0 and 1), demonstrating non-volatile optical memory functionality operating robustly up to 80 K.
- Scalability and Simplicity: The approach requires no external fields or complex nanostructure modifications (like cantilevers), offering a scalable path for integrating enhanced spin coherence into large-scale quantum systems.
- Writing Dynamics: The reconfiguration process is attributed to lattice defect diffusion, evidenced by two distinct threshold pulse energies (0.043 nJ and 0.061 nJ) matching the activation energy ratios of vacancy and self-interstitial defects in diamond.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum GS Splitting Enhancement | 1.8 | THz | Maximum observed splitting after reconfiguration. |
| Initial GS Splitting (Example SiV) | 91 | GHz | Measured splitting before pulsed laser irradiation (s1 state). |
| Reconfigured GS Splitting (Example SiV) | 270 | GHz | Measured splitting after pulsed laser irradiation (s2 state). |
| Non-Volatile Memory Operating Temp | Up to 80 | K | Temperature limit where strain shift is still > linewidth. |
| SiV Photoluminescence (PL) Lifetime | 1.9 | ns | Consistent lifetime across both strain states. |
| Writing Laser Pulse Width | 30 | ps | Picosecond pulsed laser used for strain reconfiguration. |
| Writing Laser Repetition Frequency | 60 | MHz | Used during high-power irradiation. |
| Writing Threshold Energy (Type 1) | 0.043 ± 0.011 | nJ | Lower threshold attributed to defect diffusion. |
| Writing Threshold Energy (Type 2) | 0.061 ± 0.012 | nJ | Higher threshold attributed to defect diffusion. |
| Ion Implantation Energy (28Si2+) | 70 | keV | Focused Ion Beam (FIB) implantation energy. |
| Ion Penetration Depth (SRIM) | 48 ± 12 | nm | Simulated depth of implanted Si ions. |
| Diamond Purity | 1 | ppb | Purity of the electronic-grade diamond sample (Element 6). |
| Memory Read/Write Contrast | > 6 | dB | Contrast achieved between the 0 and 1 states (PL intensity). |
| SiV Strain Sensitivity (DFT) | ~1.3 | PHz/strain | Theoretical sensitivity of SiV electronic orbital states. |
Key Methodologies
Section titled âKey MethodologiesâThe SiV centers were fabricated via focused ion beam (FIB) implantation, followed by high-temperature annealing and characterized using a low-temperature confocal microscope.
- Sample Preparation: Electronic-grade diamond (Element 6) was cleaned using a 3:1 H2SO4:H2O2 piranha solution. The top 10 ”m was removed via oxygen plasma etching to eliminate surface strain.
- Ion Implantation: 28Si2+ ions were implanted using a 100 kV FIB system at 70 keV. The fluence was set at 20 ions/spot with a 3 ”m spot pitch, resulting in a simulated penetration depth of 48 ± 12 nm.
- High-Temperature Annealing: Samples were annealed in an ultra-high vacuum (1 x 10-8 Torr) environment:
- Ramping: Temperature increased to 400 °C over 4 h (100 °C/h rate).
- Intermediate: Increased to 800 °C for an additional 4 h.
- Final: Culminated at 1200 °C for 2 h.
- Acid Cleaning: Post-annealing, samples were treated with a tri-acid mixture (H2SO4, HNO3, and HClO4) boiled and refluxed for 1.5 hours at 250 °C, followed by a final piranha cleaning step.
- Optical Characterization (Reading): Measurements were performed at approximately 8 K using a home-built confocal microscope. Photoluminescence (PL) spectra were acquired using a continuous-wave (cw) 532 nm pump laser.
- All-Optical Reconfiguration (Writing): High-power picosecond pulsed lasers (532 nm, 30 ps pulse width, 60 MHz repetition) were used to induce local crystal structure modification by triggering defect migration.
Commercial Applications
Section titled âCommercial ApplicationsâThis technology, leveraging non-volatile strain control in diamond color centers, has direct implications for several emerging high-tech sectors:
- Quantum Computing and Networking:
- Enhanced Qubit Coherence: The ability to deterministically increase Ground State (GS) splitting up to 1.8 THz significantly reduces electron spin interaction with acoustic phonons, improving spin coherence time (T2) necessary for robust quantum memories.
- Scalable Quantum Systems: The localized, non-invasive nature of the strain control offers a scalable method for creating arrays of identical, high-coherence qubits without requiring complex suspended nanostructures (e.g., cantilevers).
- Classical Data Storage:
- Non-Volatile Optical Memory: SiV centers serve as ultra-compact, high-fidelity (contrast > 6 dB) memory elements, enabling high-density data storage solutions that operate at temperatures up to 80 K.
- High-Dimensional Encoding: The observation of multiple stable strain configurations suggests potential for high-dimensional data storage (beyond binary 0/1).
- Photonic Machine Learning and Neuromorphic Computing:
- Reconfigurable Photonics: The non-volatile and reconfigurable nature of the SiV strain states provides opportunities for developing tunable nanophotonics essential for integrated optical memories and computational elements in neuromorphic hardware.
- Materials Science and Defect Engineering:
- Localized Strain Control: The method establishes a new paradigm for direct, localized manipulation of strain fields around solid-state defects, applicable to other color centers (e.g., in silicon carbide or rare-earth ions) where strain tuning is critical.
View Original Abstract
Strain engineering is vital for tuning the optical and spin properties of solid-state color centers, enhancing spin coherence and compensating emission wavelength shift. Here, we develop an all-optical approach to directly modify the local strain of color centers at the nanoscale by migrating the nearby defect. High-power pulsed optical irradiation triggers defect migration, which subsequently leads to the redistribution of the local crystal lattice of the host material. This redistribution alters the strain experienced by nearby color centers. Using silicon-vacancy centers in diamond, we validate this method and demonstrate a ground state splitting enhancement of up to 1.8 THz. Unlike conventional methods, our approach requires no external fields or nanostructure modifications, enabling non-volatile strain control and optical memory functionality across wide temperature ranges. Its local, permanent nature offers a scalable path for enhancing spin coherence in large-scale quantum systems and has potential applications in photonic machine learning.