Single-Shot Readout and Weak Measurement of a Tin-Vacancy Qubit in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-03-19 |
| Journal | arXiv (Cornell University) |
| Authors | Eric I. Rosenthal, Souvik Biswas, Giovanni Scuri, Hope Lee, Abigail Stein |
| Institutions | Stanford University, Sandia National Laboratories |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Single-Shot Readout of SnV- Qubits in Diamond
Section titled âTechnical Documentation & Analysis: Single-Shot Readout of SnV- Qubits in DiamondâExecutive Summary
Section titled âExecutive SummaryâThe analyzed research demonstrates a significant advancement in solid-state quantum computing by achieving high-fidelity single-shot readout and rapid coherent control of the Tin-Vacancy (SnV-) qubit in diamond.
- Record Readout Fidelity: Achieved 87.4% single-shot readout fidelity, the highest reported to date for an SnV- electronic spin, further boosted to 98.5% conditional fidelity.
- Rapid Coherent Control: High-fidelity readout is compatible with rapid microwave spin control, demonstrating an 80 ns $\pi$-pulse time, confirming the SnV- as a robust spin-photon interface.
- Quantum Network Viability: The SnV- platform operates favorably at elevated cryogenic temperatures (1.7 K), offering robustness against thermal decoherence compared to SiV- centers.
- Efficiency Bottleneck Identified: Measurement efficiency ($\eta$) was characterized at $\approx 0.1%$, confirming orders-of-magnitude room for improvement via integration with advanced nanophotonic structures.
- Metrological Advancement: Developed and utilized weak quantum measurement techniques to precisely characterize measurement-induced dephasing and benchmark color center spin readout efficiency.
- Material Requirement: The results rely on high-quality diamond substrates suitable for defect implantation, strain engineering, and nanophotonic fabrication (mesa structures).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, characterizing the performance of the SnV- qubit and the measurement apparatus.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Single-Shot Readout Fidelity ($F_{r}$) | 87.4 | % | Achieved using 50 ”s integration window. |
| Conditional Readout Fidelity ($F_{c}$) | 98.5 | % | Conditioned on two consecutive measurements. |
| QND-Equivalent Fidelity ($F_{q}$) | $\approx 77$ | % | Captures extent qubit remains in expected eigenstate post-measurement. |
| Microwave $\pi$-Pulse Time | 80 | ns | Rapid spin control at $B = 125$ mT. |
| Coherence Time ($T_{2}^{CPMG-2}$) | $270 \pm 30$ | ”s | Measured at $B = 125$ mT, $\zeta = 147^{\circ}$. |
| Measurement Efficiency ($\eta$) | $\approx 0.1$ | % | Overall loss between qubit and detector. |
| Cyclicity ($\Lambda$) | $2244 \pm 108$ | N/A | Ratio of spin-preserving to spin-flipping decay (maximized). |
| Saturation Power ($P_{sat}$) | $313 \pm 8$ | nW | Specified at input to cryostat (Fig. 4 fit). |
| Ground State Splitting | 903 | GHz | Moderately strained SnV- center. |
| Operating Temperature | 1.7 | K | Cryogenic environment. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment successfully combined advanced diamond material engineering with precise optical and microwave control techniques under cryogenic conditions.
- Material Preparation: The SnV- centers were created via Tin (Sn) implantation into a diamond substrate at a depth of approximately $90 \pm 20$ nm.
- Nanostructuring: The implanted region was fabricated into a mesa structure (1 ”m height) to enhance photon collection, although the authors note the emitter was found near the edge of the mesa.
- Cryogenic Operation: The system was operated at 1.7 K using a cryostat equipped with a high numerical aperture (NA 0.82) cryogenic objective for signal collection.
- Magnetic Field Alignment: A two-axis vector magnet was used to align the static magnetic field ($B$) near the spin dipole axis ($\zeta \approx 147^{\circ}$), maximizing the cyclicity ($\Lambda$) required for high-fidelity readout.
- Spin Control: Microwave pulses (e.g., 3.677 GHz) were delivered via a wire bond draped over the diamond chip to achieve rapid coherent spin manipulation.
- Readout Protocol: Single-shot readout was performed using photoluminescence (PL) detection under resonant optical drive, utilizing a 50 ”s integration window.
- Noise Mitigation: Charge Resonance Checks (CRCs) were implemented before and after readout steps to post-select data, ensuring the qubit remained in the correct charge state and minimizing spectral diffusion effects.
- Efficiency Characterization: Measurement-induced dephasing was studied by inserting a weak measurement pulse of variable power and duration into a dynamical decoupling sequence (CPMG-2), allowing for the determination of the low measurement efficiency ($\eta$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical role of high-quality, engineered diamond substrates for advancing solid-state quantum technologies. 6CCVD is uniquely positioned to supply the materials and customization required to replicate, optimize, and scale these results.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High-Purity Substrates (Minimizing background noise/defects) | Electronic Grade SCD (Single Crystal Diamond) wafers. | Provides ultra-low nitrogen content (PPM level) and minimal strain, crucial for achieving long spin coherence times ($T_{2}$) and stable SnV- operation. |
| Nanophotonic Integration (Mesa/Pillar structures, 1 ”m height) | Custom Thickness SCD Plates (0.1 ”m to 500 ”m). | We supply precisely controlled thin SCD layers, ideal for fabricating high-aspect-ratio nanophotonic devices (e.g., 1 ”m thick membranes or pillars) necessary to boost photon collection efficiency ($\eta$). |
| Large Area Scaling (Future quantum networks/arrays) | PCD Wafers up to 125 mm diameter. | Enables the scaling of SnV- quantum nodes into large, integrated arrays, moving beyond single-emitter experiments. |
| Microwave Control Integration (On-chip antennas/waveguides) | Custom Metalization Services (Au, Pt, Pd, Ti, W, Cu). | We offer in-house metal deposition and patterning to integrate optimized microwave delivery structures directly onto the diamond surface, improving Rabi frequency and control fidelity. |
| Surface Quality (Minimizing optical loss and scattering) | Ultra-Low Roughness Polishing (SCD: $R_{a} < 1$ nm; PCD: $R_{a} < 5$ nm). | Essential for high-efficiency optical coupling (NA 0.82 objective) and reducing scatter noise, which currently limits polarization fidelity. |
| Strain Engineering (Optimizing cyclicity $\Lambda$ and splitting) | Material Consultation & Custom Growth. | Our in-house PhD team provides expert consultation on material selection and growth parameters to achieve specific, controlled strain profiles, optimizing the SnV- Hamiltonian for desired operating conditions. |
| Global Logistics | Global Shipping (DDU default, DDP available). | Ensures reliable and rapid delivery of sensitive diamond materials to international research facilities and cryostat setups. |
Call to Action
Section titled âCall to ActionâThe demonstrated low measurement efficiency ($\eta \approx 0.1%$) confirms that the next major breakthrough in SnV- quantum technology relies on integrating these qubits into high-efficiency nanophotonic structures. 6CCVD provides the foundational, high-quality diamond materials and customization services necessary to achieve the projected 10x to 100x improvement in photon collection efficiency.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The negatively charged tin-vacancy center in diamond (SnV$^-$) is an emerging platform for building the next generation of long-distance quantum networks. This is due to the SnV$^-$âs favorable optical and spin properties including bright emission, insensitivity to electronic noise, and long spin coherence times at temperatures above 1 Kelvin. Here, we demonstrate measurement of a single SnV$^-$ electronic spin with a single-shot readout fidelity of $87.4%$, which can be further improved to $98.5%$ by conditioning on multiple readouts. We show this performance is compatible with rapid microwave spin control, demonstrating that the trade-off between optical readout and spin control inherent to group-IV centers in diamond can be overcome for the SnV$^-$. Finally, we use weak quantum measurement to study measurement induced dephasing; this illuminates the fundamental interplay between measurement and decoherence in quantum mechanics, and makes use of the qubitâs spin coherence as a metrological tool. Taken together, these results overcome an important hurdle in the development of the SnV$^-$ based quantum technologies, and in the process, develop techniques and understanding broadly applicable to the study of solid-state quantum emitters.