Optical driving, spin initialization and readout of single SiV− centers in a Fabry-Perot resonator
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-10-16 |
| Journal | Communications Physics |
| Authors | Gregor Bayer, Robert Berghaus, Selene Sachero, Andrea B. Filipovski, Lukas Antoniuk |
| Institutions | Université de Tours, Centre National de la Recherche Scientifique |
| Citations | 17 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”- Quantum Repeater Platform: Demonstrated a passively stable spin-photon interface utilizing single negatively charged Silicon Vacancy (SiV-) centers embedded in nanodiamonds (NDs) coupled to a Fabry-Perot (FP) microcavity, operating at 4 K.
- Coherent Optical Driving: Achieved coherent optical driving between the ground and excited states with a high Rabi frequency of 330 ± 50 MHz.
- Purcell Enhancement: Realized significant lifetime shortening, yielding a Purcell factor (Fp) of 1.61 (lower bound), corresponding to an optical lifetime of 1.0 ns.
- Fast Spin Initialization: Demonstrated all-optical electron spin initialization within 67 ns, achieving a fidelity of 80% at equilibrium.
- High-Field Operation: Successfully initialized and read out the electron spin in strong magnetic fields up to 3.2 T, enabling operation in compact vector magnets.
- Scalability Potential: The platform establishes a promising building block for quantum repeater nodes, offering efficient mode-matching to fiber networks and potential for ms-range spin coherence times necessary for long-distance quantum communication.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Operating Temperature | 4 | K | Liquid Helium bath |
| Maximum Magnetic Field (B) | 3.2 | T | Used for spin initialization/readout |
| Rabi Frequency (ΩR/2π) | 330 ± 50 | MHz | Coherent optical driving |
| Optical Lifetime (τcav) | 1.0 ± 0.5 | ns | Measured under strong drive |
| Purcell Factor (Fp) | 1.61 | - | Lower bound, extrapolated |
| Spin Initialization Time (Tinit) | 67 ± 6 | ns | All-optical initialization speed |
| Spin Initialization Fidelity | 80 ± 4 | % | At equilibrium |
| Electron Spin Lifetime (Tspin) | 350 ± 40 | ns | Measured at 3.2 T (limited by field misalignment) |
| Zero-Power Linewidth (min) | 107 | MHz | Measured at cavity mode m=11 |
| Cavity Quality Factor (Q) | 22,000 to 30,000 | - | Depending on effective length (m=8 to m=11) |
| Cavity Finesse (Fexp) | 2700 ± 500 | - | After ND placement |
| Ideal Finesse (Fideal) | 6300 | - | Coating-limited value |
| Scattering Loss (ND interface) | 85 | ppm | Per round trip |
| Spherical Mirror RoC | 8 | µm | Radius of Curvature |
| Nanodiamond Size (Lateral) | 200 - 300 | nm | Used for coupling |
| Cavity Mode Volume (V) | 5.2 to 7.5 | (µm)3 | Depending on effective length (m=8 to m=11) |
| B-factor (β) | 38 | % | Fraction of excited state population decaying coherently into cavity mode (lower bound) |
| DC Field Sensitivity (Estimated) | 180 ± 60 | mT Hz-1/2 | Based on B-field dependent splitting fit accuracy |
Key Methodologies
Section titled “Key Methodologies”- SiV- Nanodiamond (ND) Synthesis: NDs were created using High-Pressure High-Temperature (HPHT) treatment of a mixture of naphthalene (C10H8) and tetrakis(trimethylsilyl)silane (C12H36Si5).
- ND Purification and Sizing: Purification involved using an acid mixture (HNO3, HClO4, and H2SO4). Final ultrasonic treatment yielded crystals sized between 40 and 500 nm.
- Mirror Fabrication: Distributed Bragg Reflectors (DBRs) were coated onto silica substrates. The spherical mirror (RoC ≈ 8 µm) was fabricated using Focused Ion Beam (FIB) milling to achieve low surface roughness (< 0.2 nm).
- ND Placement (Nanomanipulation): Pre-characterized NDs (200-300 nm) were precisely transferred to the center of the curved FP mirror using an Atomic Force Microscope (AFM)-based pick-and-place technique.
- Cryogenic Operation and Stability: The open FP cavity was immersed directly in a liquid Helium bath (4 K), providing high cooling power and passive mechanical stability, limiting length fluctuations to less than one linewidth (160 pm).
- Optical Excitation: Resonant excitation was performed using an actively stabilized Ti:sapphire ring laser (around 737 nm). Pulsed excitation for spin measurements was controlled by an FPGA driving a fiber-pigtailed amplitude electro-optical modulator.
- Spin Control: A strong external magnetic field (up to 3.2 T) was applied along the cavity axis to split the spin-orbit states, enabling all-optical initialization and readout by resonantly pumping the spin-conserving transition (C3).
Commercial Applications
Section titled “Commercial Applications”- Quantum Communication Networks: Realization of modular quantum repeater nodes capable of linking quantum memories with flying qubits, overcoming signal attenuation limits in optical fibers over hundreds of kilometers.
- Integrated Quantum Photonics: Development of scalable, stable spin-photon interfaces serving as fundamental building blocks for complex quantum circuits and processors.
- High-Field Quantum Sensing: Utilization of the SiV-/cavity platform as a compact sensor for measuring DC magnetic field strengths in high-field environments (e.g., large superconducting magnets), requiring only a tunable laser rather than complex high-frequency microwave sources (100 GHz).
- Cryogenic Quantum Hardware: Manufacturing and integration of passively stable, low-volume Fabry-Perot microcavity systems designed for operation in liquid Helium environments (4 K).
- Advanced Nanodiamond Materials: Production of high-quality, size-controlled nanodiamonds containing spectrally stable SiV- centers for use in solid-state quantum memory and light emission applications.
View Original Abstract
Abstract Large-scale quantum communication networks require quantum repeaters due to the signal attenuation in optical fibers. Ideal quantum repeater nodes efficiently link a quantum memory with photons serving as flying qubits. Color centers in diamond, particularly the negatively charged silicon vacancy center, are promising candidates to establish such nodes. Inefficient connection between the color center’s spin to the optical fiber networks is a major obstacle, that could be resolved by utilizing optical resonators. Here, we couple individual silicon vacancy centers incorporated in a nanodiamond to a hemispherical, stable Fabry-Perot microcavity, achieving Purcell-factors larger than 1. We demonstrate coherent optical driving between ground and excited state with a Rabi-frequency of 330 MHz, all-optical initialization and readout of the electron spin in magnetic fields of up to 3.2 T. Spin initialization within 67 ns with a 80 % fidelity and a lifetime of 350 ns are reached. Our demonstration opens the way to realize quantum repeater applications.