Time-space-encoded readout for noise suppression and scalable scanning in optically active solid-state spin systems
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-06-06 |
| Journal | Physical Review Applied |
| Authors | Joachim P. Leibold, Nick R. von Grafenstein, Xiaoxun Chen, Linda MĂŒller, Karl D. Briegel |
| Institutions | Technical University of Munich, Munich Center for Quantum Science and Technology |
| Analysis | Full AI Review Included |
Technical Documentation: Time-Space-Encoded Readout (T2S) for Scalable Quantum Sensing
Section titled âTechnical Documentation: Time-Space-Encoded Readout (T2S) for Scalable Quantum Sensingâ6CCVD Analysis of Physical Review Applied 23, 064018 (2025)
Executive Summary
Section titled âExecutive SummaryâThis research introduces the Time-to-Space (T2S) encoding readout scheme, leveraging high-quality MPCVD diamond and Acousto-Optic Modulators (AOMs) to revolutionize data acquisition in solid-state spin systems.
- Core Innovation: T2S decouples microwave (MW) spin manipulation from rapid optical readout, enabling multiple spatially resolved measurements within the spin systemâs T1 lifetime.
- Material Focus: Demonstrated using Nitrogen-Vacancy (N-V) center ensembles in high-purity Single Crystal Diamond (SCD).
- Noise Reduction: Achieved efficient common-mode noise cancellation, resulting in a 60% reduction in the noise floor and a 3x increase in Signal-to-Noise Ratio (SNR) in N-V-NMR experiments.
- Scalability & Speed: Enables scalable multipixel scanning/imaging, potentially accelerating data acquisition by several hundred times compared to conventional scanning methods.
- Readout Speed: Achieved rapid readout cycles of 2.5 ”s per spot (2 ”s laser pulse + 0.5 ”s spot movement), significantly faster than typical T1 relaxation times (ms range).
- Future Potential: The scheme is readily applicable to other quantum defects (SiC, h-BN) and single spin-defect experiments, requiring only standard ODMR components.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, focusing on material performance and system throughput:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| N-V Layer Thickness (Shallow) | ~5 | nm | Used for T1 and XY8 measurements. |
| N-V Layer Thickness (Thick) | ~10 | ”m | Used for high-sensitivity CASR/NMR. |
| T1 Relaxation Time (Plain Diamond) | 1.1 ± 0.05 | ms | Reference spot performance. |
| T1 Relaxation Time (Mn2+ Coated) | 0.5 ± 0.03 | ms | Sample spot performance (reduced T1). |
| SNR Improvement (NMR) | 3 | x | Achieved via common-mode noise subtraction. |
| Noise Reduction (Noise Floor) | 60 | % | Reduction attributed to MW phase noise cancellation. |
| Readout Time per Spot | 2.5 | ”s | Includes 2 ”s laser pulse and 0.5 ”s spot movement. |
| Maximum Readouts (T1 limited, 1 ms) | 400 | spots | Theoretical maximum for long pulse sequences. |
| Maximum Readouts (T2 limited, 100 ”s) | 40 | spots | Achievable for shorter pulse sequences. |
| AOM Active Aperture | 0.25 | mm | Limits maximum beam diameter. |
| AOM Acoustic Velocity (Quartz) | 5.7 | mm/”s | Used for fast scanning implementation. |
| Laser Wavelength | 532 | nm | Green excitation source. |
Key Methodologies
Section titled âKey MethodologiesâThe T2S scheme relies on precise material engineering and high-speed optical control, implemented as follows:
- Material Preparation: High-purity diamond was used, featuring N-V ensembles created via nitrogen implantation (2.5 keV, 2 x 1012/cm2) to achieve near-surface (shallow, ~5 nm) or thick (~10 ”m) N-V layers, depending on the sensing application (T1/XY8 vs. NMR).
- Homogeneous MW Control: A simple loop antenna or resonator was used to ensure uniform MW fields across the entire region of interest, allowing simultaneous spin manipulation of all target spots.
- Fast Optical Scanning (T2S Encoding): The conventional single-tone RF input of the Acousto-Optic Modulator (AOM) driver was replaced with a train of pulses of different RF frequencies.
- Position-Time Linkage: Each distinct RF frequency drives the AOM to a specific deflection angle, linking the time of the optical readout pulse to a specific spatial position (spot S1, S2, etc.) on the diamond surface.
- High-Speed Readout: The AOMâs fast response time (nanosecond scale) allows the laser spot to be moved and fluorescence read out in 2.5 ”s cycles, ensuring multiple readouts occur faster than the N-V T1 relaxation time (milliseconds).
- Noise Cancellation: By simultaneously manipulating and subsequently reading out two or more spatially separated spots (one sample, one reference), common-mode noise sources (e.g., magnetic field drifts, MW phase noise) are correlated and efficiently canceled via time-domain data subtraction.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe T2S encoding scheme demands ultra-high-quality diamond substrates with precise defect engineering and surface preparation. 6CCVD is uniquely positioned to supply the foundational materials required to replicate, scale, and advance this research.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the high SNR and long coherence times necessary for advanced quantum sensing, the following 6CCVD materials are recommended:
| Research Requirement | 6CCVD Material Solution | Technical Specification Match |
|---|---|---|
| High Purity Substrates | Optical Grade SCD | SCD ensures minimal native defects and low strain, critical for maximizing T1 and T2 times. |
| Shallow N-V Ensembles | Custom Implanted SCD | We supply SCD wafers ready for low-energy implantation (e.g., 2.5 keV) to create near-surface N-V layers (down to 5 nm depth) for surface-sensitive NMR/relaxometry. |
| Thick N-V Layers | High-Growth Rate SCD | We provide SCD plates with controlled nitrogen incorporation during growth, achieving homogeneous N-V layers up to 500 ”m thick, ideal for high-sensitivity ensemble sensing (as used in the CASR experiments). |
| Scalable Imaging Area | Large Area PCD | For future large-scale imaging, we offer Polycrystalline Diamond (PCD) plates up to 125 mm diameter with high uniformity and low surface roughness (Ra < 5 nm). |
| Microfluidic Integration | Ultra-Smooth SCD | We guarantee SCD polishing to Ra < 1 nm, ensuring optimal optical coupling and compatibility with microfluidic bonding and surface functionalization layers. |
Customization Potential
Section titled âCustomization PotentialâThe T2S scheme, especially when scaled to 2D scanning using AODs (as discussed in Appendix G), requires highly customized components. 6CCVD offers comprehensive engineering services to meet these demands:
- Custom Dimensions: We provide plates and wafers in custom sizes and shapes, essential for integrating diamond chips into complex optical setups (e.g., F-Ξ lens systems, 4f configurations) and microfluidic platforms.
- Advanced Metalization: While the paper did not detail on-chip metalization for MW delivery, 6CCVD offers in-house deposition of standard contacts (Au, Pt, Ti, Pd, Cu, W). This is crucial for fabricating high-performance on-chip microwave antennas or resonators (as referenced in the paper) directly onto the SCD surface.
- Thickness Control: We offer precise control over substrate thickness, from 0.1 ”m SCD membranes (for ultimate proximity sensing) up to 10 mm thick substrates (for robust thermal management and handling).
Engineering Support
Section titled âEngineering SupportâThe successful implementation of T2S relies on optimizing the diamond material properties (T1, T2) relative to the optical scanning speed (AOM/AOD performance).
6CCVDâs in-house PhD team specializes in the physics of N-V centers and can assist researchers with material selection and specification for similar Quantum Sensing and High-Speed Imaging projects. We ensure that the chosen diamond grade and defect density are optimized for the required pulse sequence duration and target SNR.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Optically active solid-state spin systems have been extensively studied in quantum technologies. We introduce a new readout scheme, termed âtime-to-spaceâ (T2S) encoding, which decouples spin manipulation from optical readout both temporally and spatially. This is achieved by simultaneously controlling the spin state within a region of interest, followed by rapid scanning of the optical readout position using an acousto-optic modulator. Time tracking allows the optical readout position to be encoded as a function of time. Using nitrogen-vacancy center ensembles in diamond, we demonstrate that the T2S scheme enables correlated experiments for efficient common-mode noise cancellation in various nano- and microscale sensing scenarios. Additionally, we show scalable multipixel imaging that does not require a camera and has the potential to accelerate data acquisition by several hundred times compared to conventional scanning methods. We anticipate widespread adoption of this technique, as it requires no additional components beyond those commonly used in experiments with optically adressable spin systems.