Spin Dynamics of a Solid-State Qubit in Proximity to a Superconductor
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-01-05 |
| Journal | Nano Letters |
| Authors | Richard Monge, Tom Delord, Nicholas V. Proscia, Zav Shotan, Harishankar Jayakumar |
| Institutions | Japan Advanced Institute of Science and Technology, City College of New York |
| Citations | 15 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Spin Dynamics in Diamond-Superconductor Hybrids
Section titled âTechnical Documentation & Analysis: Spin Dynamics in Diamond-Superconductor HybridsâThis document analyzes the research paper âSpin dynamics of a solid-state qubit in proximity to a superconductorâ to provide technical specifications and highlight how 6CCVDâs advanced MPCVD diamond materials and fabrication services are essential for replicating and extending this cutting-edge research in hybrid quantum systems and nanoscale noise spectroscopy.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the use of a shallow Nitrogen-Vacancy (NV) center in an all-diamond scanning probe to investigate the spin dynamics near a high-critical-temperature (high-Tc) superconductor (TBCCO).
- Coherence Enhancement: Proximity to the TBCCO film significantly extends the NV spin coherence lifetime (T2,HE), increasing it from 28.3 ”s (off-superconductor) to 42.8 ”s (on-superconductor) at 69 K.
- Noise Suppression Mechanism: The T2 enhancement is tentatively rationalized as the suppression of electric field noise originating from fluctuating charge carriers on the diamond surface, induced by the presence of the superconductor.
- Material Requirements: The experiment relies critically on ultra-low-noise Single Crystal Diamond (SCD) hosting shallow NV centers (60-79 nm measured depth) and precise control over diamond surface termination (e.g., high-resistivity oxygen termination).
- Advanced Sensing: The methodology enables T2-weighted transverse relaxometry, demonstrating a novel imaging modality for mapping the boundaries and noise profiles of superconducting films at the nanoscale.
- Hybrid Quantum Relevance: These findings pave the way for integrating solid-state qubits (NV centers) with superconducting circuits, offering potential for long-lived quantum memories and microwave-to-optical interfaces.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and methodology described in the paper.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Superconductor Material | Tl2Ba2CaCu2O8 (TBCCO) | N/A | High-Tc film on LAO substrate |
| Critical Temperature (Tc) | 105 | K | TBCCO film transition temperature |
| Operating Temperature (T) | 69 | K | Cryogenic measurement temperature |
| TBCCO Film Thickness | 500 | nm | Sample dimension |
| NV Center Depth (Measured Range) | 60 - 79 | nm | Effective depth of shallow NV probes |
| Tip-Surface Distance (Coherence) | 150 | nm | Distance maintained during T2,HE scans |
| Hahn-Echo Lifetime (T2,HE) - Off SC | 28.3 ± 3.0 | ”s | Measured away from superconductor |
| Hahn-Echo Lifetime (T2,HE) - On SC | 42.8 ± 2.9 | ”s | Measured proximal to superconductor |
| Coherence Enhancement Factor | ~1.5 | N/A | Ratio of T2,HE (On SC / Off SC) |
| Applied Magnetic Field (BM) | ~6 | mT | Uniform field for Zeeman splitting |
| Diamond Surface Resistivity (Calculated) | 10-10 - 10-17 | Ohm-1s-1 | Range for oxygen-terminated diamond |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a complex, integrated cryo-scanning probe setup combining atomic force microscopy (AFM) and confocal/ODMR techniques.
- Material Integration: An all-diamond scanning probe (commercial Qnami tip) hosting shallow NV centers was positioned proximal to a micro-patterned TBCCO film on a Lanthanum Aluminate (LAO) substrate.
- Cryogenic Environment: Experiments were conducted in a closed-cycle cryo-workstation at T = 69 K, well below the TBCCO critical temperature (Tc = 105 K).
- Optical and Microwave Control: NV centers were initialized and read out using a 532 nm continuous-wave (cw) laser and manipulated using pulsed microwave (mw) excitation delivered via a 25 ”m copper wire antenna.
- Spin Coherence Measurement: Time-resolved magnetometry protocols, including Hahn-echo (HE) and CPMG sequences, were used to measure the transverse relaxation time (T2,HE) and characterize the local noise environment.
- Vector Magnetometry: ODMR measurements using two differently-oriented NVs were combined with ancillary coil fields to reconstruct the full vector magnetic field (BM) and confirm that the T2 enhancement was not due to changes in BM.
- T2 Imaging Protocol: A specialized microwave recalibration protocol was implemented during scanning to dynamically adjust mw frequency and power, ensuring constant spin rotation and enabling the reconstruction of a one-dimensional T2-weighted relaxometry image across the superconductor boundary.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and advancement of this research require diamond materials with exceptional purity, precise defect engineering, and advanced surface controlâall core specialties of 6CCVD.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the high coherence times and surface sensitivity required for this nanoscale noise spectroscopy, 6CCVD recommends the following materials:
| Research Requirement | 6CCVD Material Recommendation | Technical Rationale |
|---|---|---|
| High Coherence NV Host | Optical Grade Single Crystal Diamond (SCD) | Ultra-low nitrogen concentration ([N] < 1 ppb) minimizes bulk spin noise (e.g., 14N/15N P1 centers), maximizing intrinsic T2 and T1 coherence times necessary for sensitive qubit operation. |
| Shallow NV Sensing | Custom Ion Implantation Services | Precise control over NV depth (down to 0.1 ”m SCD thickness) and concentration, using either 14N or 15N, is critical for maximizing sensitivity to surface noise sources (electric and magnetic) and achieving optimal T2 enhancement. |
| Noise Environment Control | Advanced Surface Termination | 6CCVD offers tailored surface treatments (e.g., Oxygen, Hydrogen, or Fluorine termination) to precisely control the surface resistivity and manage fluctuating charge carriers, directly addressing the primary noise source identified in the paper. |
| Future Scaling/Integration | Polycrystalline Diamond (PCD) Wafers | For large-scale integration with superconducting circuits, 6CCVD provides PCD wafers up to 125 mm diameter, polished to Ra < 5 nm, offering a robust platform for hybrid device manufacturing. |
Customization Potential
Section titled âCustomization PotentialâThe complexity of the scanning probe geometry and the need for on-chip microwave delivery necessitate specialized fabrication capabilities, which 6CCVD provides in-house:
- Custom Dimensions and Geometry: The experiment utilized a specific diamond pillar/cantilever probe geometry. 6CCVD offers precision laser cutting and etching services to fabricate custom SCD plates and wafers (up to 500 ”m thick) into complex shapes required for specialized scanning probe setups.
- Microwave Antenna Integration: The pulsed protocols rely on a copper wire antenna near the NV center. 6CCVD provides internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for depositing high-quality, low-loss metal contacts and microwave transmission lines directly onto the diamond surface, ensuring efficient spin manipulation.
- Substrate Thickness: While the paper used a 500 nm TBCCO film, 6CCVD can supply SCD substrates up to 500 ”m thick and PCD substrates up to 10 mm thick, providing robust platforms for complex multi-layer hybrid structures.
Engineering Support
Section titled âEngineering SupportâThe paper highlights the complex interplay between electric noise, magnetic noise, and surface dynamicsâa challenge requiring deep material science expertise.
6CCVDâs in-house PhD team specializes in defect engineering, surface physics, and noise spectroscopy in diamond quantum materials. We can assist researchers in:
- Material Selection: Optimizing the SCD grade and thickness based on target coherence times and operating temperatures (e.g., 69 K cryogenic environment).
- NV Engineering: Designing the optimal implantation recipe (energy, dose, annealing) to achieve the required shallow NV depth (60-79 nm) while minimizing implantation damage.
- Surface Optimization: Consulting on the appropriate surface termination to achieve the desired surface resistivity and maximize noise suppression for similar Hybrid Quantum Device projects.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).
View Original Abstract
A broad effort is underway to understand and harness the interaction between superconductors and spin-active color centers with an eye on hybrid quantum devices and novel imaging modalities of superconducting materials. Most work, however, overlooks the interplay between either system and the environment created by the color center host. Here we use a diamond scanning probe to investigate the spin dynamics of a single nitrogen-vacancy (NV) center proximal to a superconducting film. We find that the presence of the superconductor increases the NV spin coherence lifetime, a phenomenon we tentatively rationalize as a change in the electric noise due to a superconductor-induced redistribution of charge carriers near induced redistribution of charge carriers near the NV. We then build on these findings to demonstrate transverse-relaxation-time-weighted imaging of the superconductor film. These results shed light on the dynamics governing the spin coherence of shallow NVs, and promise opportunities for new forms of noise spectroscopy and imaging of superconductors.