Tin-Vacancy Centers in Diamond for Quantum Network
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | The Review of Laser Engineering |
| Authors | Takayuki Iwasaki |
| Institutions | Tokyo Institute of Technology |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research investigates Tin-Vacancy (SnV) centers in diamond as next-generation solid-state quantum emitters, focusing on overcoming the limitations of existing Group-IV centers (SiV, GeV) for quantum network applications.
- Core Value Proposition: SnV centers exhibit a large ground state splitting (ÎGS â 850 GHz) due to the heavy Sn atomâs strong spin-orbit interaction. This significantly suppresses phonon absorption, promising long spin coherence times (T2) at accessible Kelvin temperatures.
- Performance Benchmark: Initial spin dephasing time (T2*) was measured at 540 ns at 2.9 K, which is already superior to SiV and GeV centers measured at similar temperatures.
- Optical Quality: The SnV center shows a sharp Zero Phonon Line (ZPL) at 619 nm and achieves a Fourier-limit linewidth of approximately 18 MHz, indicating high optical coherence.
- Material Processing: High-quality SnV centers require high-temperature annealing (2000 °C or greater) after Sn introduction.
- Future Focus (Spin): The immediate goal is to demonstrate long T2 using advanced spin echo techniques (Hahn echo, CPMG, XY8 sequences) and material engineering (e.g., 12C enrichment).
- Future Focus (Optical): Development is required for precise control over the emission wavelength and polarization of multiple emitters to achieve quantum indistinguishability, verified through Hong-Ou-Mandel (HOM) interference.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Formation Temperature | 2000 or greater | °C | Required annealing temperature for high-quality SnV centers. |
| Zero Phonon Line (ZPL) Wavelength | 619 | nm | Observed in ensemble PL spectrum at room temperature. |
| Ground State Splitting (ÎGS) | 850 | GHz | Measured via low-temperature PL fine structure; large value suppresses phonon coupling. |
| Spin Dephasing Time (T2*) | 540 | ns | Measured at 2.9 K using CW-ODMR. |
| Fourier Limit Linewidth | 18 | MHz | Derived from excited state lifetime, indicating high optical coherence. |
| SnV Symmetry | D3d | N/A | Determined by first-principles calculation (Inversion symmetry). |
| SiV Coherence Time (Reference) | 13 | ms | Achieved only at millikelvin temperatures (requires dilution refrigerator). |
| NV Center ZPL Efficiency | 4 | % | Low efficiency limits NV use in quantum networks. |
| Target Isotope Purity | 99 | % | Target 12C enrichment to suppress nuclear spin noise from 13C. |
Key Methodologies
Section titled âKey Methodologiesâ- SnV Center Creation: Sn atoms are introduced into the diamond lattice, followed by high-temperature annealing (2000 °C or greater) to form stable, high-quality SnV centers.
- Optical Characterization: Photoluminescence (PL) spectroscopy is used to identify the sharp ZPL (619 nm) and measure the optical quality, including the Fourier-limit linewidth (18 MHz).
- Ground State Splitting Determination: Low-temperature PL measurements are performed to resolve the fine structure of the energy levels, confirming the large ground state splitting (ÎGS â 850 GHz).
- Spin Dephasing Measurement (T2*): Continuous Wave Optically Detected Magnetic Resonance (CW-ODMR) is used at Kelvin temperatures (e.g., 2.9 K) to measure the spin dephasing time (T2*).
- True Coherence Measurement (T2): Pulsed microwave sequences (Hahn echo, Carr-Purcell-Meiboom-Gill (CPMG), and XY8) are applied between initialization and readout laser pulses to measure the true spin coherence time (T2) by decoupling the spin from environmental noise.
- Wavelength Control and Tuning: Techniques such as applying mechanical strain or utilizing p-n junction device structures are employed to precisely tune the emission wavelength of the SnV centers.
- Quantum Indistinguishability Testing: Hong-Ou-Mandel (HOM) interference measurements are conducted using photons emitted from two spatially separated SnV centers to verify that their quantum properties (wavelength, linewidth, polarization) are identical.
- Material Improvement: Synthesis of diamond using 12C-enriched source gas is necessary to minimize the concentration of 13C nuclear spins, which are a primary source of decoherence.
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Networks and Repeaters: SnV centers serve as robust quantum memory nodes (qubits) and single-photon emitters, enabling the construction of long-distance, secure quantum communication networks.
- Solid-State Quantum Computing: The long spin coherence time (T2) at higher temperatures makes SnV centers viable solid-state qubits, simplifying cryogenic requirements compared to millikelvin systems.
- Integrated Quantum Photonics: SnV centers can be integrated into diamond nanostructures (e.g., waveguides, photonic crystals) to create scalable, on-chip quantum circuits for processing and routing quantum information.
- High-Fidelity Single Photon Sources (SPS): Manufacturing reliable, high-brightness SPS devices operating efficiently in the visible spectrum (619 nm) for use in quantum cryptography and metrology.
- Quantum Sensing: Utilizing the spin state of the SnV center for highly sensitive measurements (e.g., magnetic fields, temperature) that benefit from the emitterâs stability and reduced phonon coupling.
View Original Abstract
Quantum emitters in diamond are a promising candidate for quantum network applications. Here, we show basic properties of tin-vacancy (SnV) centers in diamond, which we recently discovered. The SnV center shows a sharp zero phonon line and a high fluorescence intensity. The SnV center has a possibility to have a long spin coherence time in the Kelvin temperature range, in contrast to other group-IV color centers, i.e. silicon-vacancy and germanium-vacancy centers. We discuss important experiments regarding spin and optical properties of the SnV quantum emitter for further development towards quantum network.