| Metadata | Details |
|---|
| Publication Date | 2020-02-25 |
| Journal | Physical Review Letters |
| Authors | A. R. COOPER, Won Kyu Calvin Sun, Jean-Christophe Jaskula, Paola Cappellaro |
| Institutions | California Institute of Technology, Massachusetts Institute of Technology |
| Citations | 26 |
| Analysis | Full AI Review Included |
This research demonstrates a systematic approach to scale quantum devices by identifying and controlling environmental spin defects (X spins) surrounding a Nitrogen-Vacancy (NV) center in isotopically-purified diamond.
- Core Achievement: Successfully identified, located, and characterized two previously unknown electron-nuclear spin defects (X1 and X2) in the immediate environment of a single NV quantum probe.
- Methodology: Employed rotational double electron-electron resonance spectroscopy (SEDOR) and Electron Spin Echo Envelope Modulation (ESEEM) to extract the full hyperfine and dipolar tensor parameters.
- Defect Location: The defects were spatially located relative to the NV center: X1 at 9.23 nm and X2 at 6.58 nm.
- Material Basis: Defects were created via 15N ion implantation (14 keV energy, 1013 cm-2 dose) into 99.999% 12C enriched CVD diamond.
- Quantum Control: Demonstrated precise control over the three-spin system (NV, X1, X2) and successfully created quantum coherence among the three electron spins.
- Future Impact: This approach provides a blueprint for assembling robust, multi-spin quantum registers necessary for scalable quantum information processing and quantum-enhanced sensing applications.
| Parameter | Value | Unit | Context |
|---|
| NV Zero-Field Splitting (Î) | 2Ï Â· 2870 | MHz | NV center electron spin ground state |
| Diamond Isotopic Purity | 99.999 | % | 12C enrichment level |
| Implantation Ion Species | 15N | N/A | Used for creating NV centers and defects |
| Implantation Energy | 14 | keV | 15N ion implantation energy |
| Implantation Dose | 1013 | cm-2 | 15N ion implantation dose |
| Nano-aperture Diameter | 30 | nm | Used for confined ensemble implantation |
| Annealing Temperature | 800 | °C | Annealing time: 4 hours (to mobilize vacancies) |
| Mean Implantation Depth | 19.9 | nm | Simulated depth of substitutional N defects |
| X1 Distance from NV (r1) | 9.23 ± 0.03 | nm | Estimated spatial location |
| X2 Distance from NV (r2) | 6.58 ± 0.03 | nm | Estimated spatial location |
| X1 Hyperfine A℠| 17.2 ± 0.3 | MHz | Axially symmetric tensor component |
| X1 Hyperfine A|| | 29.4 ± 0.2 | MHz | Axially symmetric tensor component |
| X2 Hyperfine A℠| 1.6 ± 0.3 | MHz | Axially symmetric tensor component |
| X2 Hyperfine A|| | 11.2 ± 0.2 | MHz | Axially symmetric tensor component |
| Dipolar Constant (dc) | 2Ï Â· 52.041 | kHz | Dipolar coupling for two electron spins at 1 nm distance |
| E-Beam Lithography Dose | 1400 | ”C/cm2 | Used to pattern nano-apertures |
| SiO2 Layer Thickness | 10 | nm | Used to mitigate ion channeling |
- Diamond Preparation: A single crystal CVD diamond substrate (100 ”m 12C layer on a 300 ”m electron grade substrate) was cleaned using boiling acid.
- Channeling Mitigation: A 10-nm SiO2 layer was deposited, followed by a 150 nm PMMA resist layer and thermally evaporated Au.
- Patterning: Electron-beam lithography (1400 ”C/cm2 dose) was used to pattern 30 nm diameter nano-aperture arrays in the resist stack.
- Ion Implantation: 15N ions were implanted through the apertures at 14 keV energy and a dose of 1013 cm-2 to create confined ensembles of defects.
- Defect Activation: The sample was annealed at 800 °C for 4 hours to promote vacancy mobility and form NV centers (low conversion efficiency).
- Surface Cleaning: Final cleaning involved a boiling mixture of concentrated acids (H2SO4:HNO3:HClO4 1:1:1) and routine piranha acid solution (H2O2:H2SO4 3:1).
- Magnetic Field Calibration: The static magnetic field strength (B0) and orientation (Ξ, Ï) were precisely determined by measuring the NV electron spin resonance frequency (cw-ESR) and resolving spectral ambiguity using ESEEM spectroscopy of the host 15N nuclear spin.
- Defect Characterization and Location: Double electron-electron resonance (SEDOR) spectroscopy was performed across various magnetic field orientations. The resulting hyperfine and dipolar coupling strengths were fitted to parametric equations (tomographic reconstruction) to estimate tensor parameters and calculate the spatial coordinates (r, ζ, Ο) of X1 and X2.
- Quantum Control: The three-spin system was initialized using Hartmann-Hahn cross-polarization. CNOT gates were implemented using a recoupled spin-echo sequence to generate three-spin coherence, which was then detected via phase-modulated disentangling gates.
| Industry/Field | Application | Relevance to Paper |
|---|
| Quantum Computing | Scalable Quantum Registers | The ability to identify, locate, and control multiple environmental spins (X1, X2) allows for the assembly of larger, addressable quantum registers beyond the single NV center. |
| Quantum Sensing (Magnetometry) | Enhanced Sensor Sensitivity | Controlling environmental spins enables their use as auxiliary quantum resources, potentially leading to quantum-enhanced sensing protocols and improved sensitivity for detecting time-varying magnetic fields. |
| Solid-State Materials Science | Defect Engineering & Identification | Provides a systematic spectroscopic approach to characterize unknown electron-nuclear spin defects in solids, aiding in understanding defect formation mechanisms (e.g., nitrogen- or silicon-related centers from implantation). |
| Quantum Communication | Quantum Repeater Nodes | The controlled multi-spin system can serve as a quantum memory or repeater node, facilitating the transfer of quantum information between distant registers. |
| Surface Science | Molecular Structure Probing | The methodology is applicable to identifying complex spin systems, including unknown molecular structures or impurities placed near the diamond surface, relevant for nanoscale NMR. |
View Original Abstract
We experimentally demonstrate an approach to scale up quantum devices by harnessing spin defects in the environment of a quantum probe. We follow this approach to identify, locate, and control two electron-nuclear spin defects in the environment of a single nitrogen-vacancy center in diamond. By performing spectroscopy at various orientations of the magnetic field, we extract the unknown parameters of the hyperfine and dipolar interaction tensors, which we use to locate the two spin defects and design control sequences to initialize, manipulate, and readout their quantum state. Finally, we create quantum coherence among the three electron spins, paving the way for the creation of genuine tripartite entanglement. This approach will be useful in assembling multispin quantum registers for applications in quantum sensing and quantum information processing.