Coherence Properties and Quantum Control of Silicon Vacancy Color Centers in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-09-28 |
| Journal | physica status solidi (a) |
| Authors | Jonas Nils Becker, Christoph Becher, Jonas Nils Becker, Christoph Becher |
| Institutions | Saarland University, University of Oxford |
| Citations | 66 |
| Analysis | Full AI Review Included |
Coherence and Quantum Control of SiV Centers in Diamond: Material Requirements for QIP Scaling
Section titled âCoherence and Quantum Control of SiV Centers in Diamond: Material Requirements for QIP ScalingâTechnical Documentation & Sales Enablement based on Becker, J.N. et al. (2017)
Executive Summary
Section titled âExecutive SummaryâThis paper thoroughly investigates the negatively charged Silicon Vacancy ($\text{SiV}^-$) center, confirming its critical role as a solid-state qubit candidate due to highly favorable optical characteristics, presenting a strong alternative to the Nitrogen Vacancy ($\text{NV}^-$) center for quantum information processing (QIP).
- Superior Optical Properties: The $\text{SiV}^-$ exhibits narrow Zero Phonon Line (ZPL) transitions and weak phonon sidebands, enabling the generation of indistinguishable photons, essential for scalable quantum networks.
- Coherent Control Achieved: Both microwave-based (Rabi oscillations, Ramsey interference) and ultrafast all-optical (12 ps pulses) techniques are demonstrated, providing full quantum control over the orbital and spin degrees of freedom.
- Decoherence Limitation Identified: Ground state spin coherence time ($\text{T}_2$) is currently limited to $45 \text{ ns}$ - $115 \text{ ns}$ at 4K, predominantly constrained by phonon-mediated transitions corresponding to the $48 \text{ GHz}$ orbital splitting.
- Material Engineering is Key: Future scalability depends on engineering the phonon environment, including application of custom crystal strain (NEMS) or fabrication of phononic crystal band gap structures (requiring $60 \text{ nm}$ diamond membranes).
- High Quantum Metrics: The bulk $\text{SiV}^-$ centers analyzed showed a high quantum efficiency ($\Phi$) of $29.6(7)%$ and a transition dipole moment ($\mu$) of $14.3(2) \text{ Debye}$.
- 6CCVD Value Proposition: Replicating and scaling this research requires ultra-pure Single Crystal Diamond (SCD), precise Si doping, and advanced nanofabrication capabilitiesâall core services offered by 6CCVD.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| SiV Point Group Symmetry | $\text{D}_{3\text{d}}$ | N/A | Trigonal-antiprismatic molecular structure. |
| Orbital Ground State Splitting ($\delta_{\text{g}}$) | $2\pi \cdot 48$ | GHz | Key frequency target for phonon suppression (corresponds to 2.3K). |
| Orbital Excited State Splitting ($\delta_{\text{g}}$) | $2\pi \cdot 259$ | GHz | |
| Spin Coherence Time ($\text{T}_2$) | $45$ to $115(9)$ | ns | Measured at 4.2K using CPT and Ramsey interference. |
| Improved Spin Relaxation ($\text{T}^{\text{spin}}_1$) | $2.5$ | ”s | Achieved using NEMS strain to increase splitting up to $470 \text{ GHz}$. |
| Optical Rabi Oscillation ($\pi$ pulse) | $12$ | ps | Pulse length used for ultrafast coherent orbital control. |
| Microwave Rabi Frequency | $\approx 15$ | MHz | Requires $\approx 40 \text{ ns}$ pulse length for $\pi$ rotation. |
| Quantum Efficiency ($\Phi$) | $29.6(7)$ | % | Calculated from measured fluorescence lifetime ($\tau=1.85 \text{ ns}$). |
| Transition Dipole Moment ($\mu$) | $14.3(2)$ | Debye | Calculated from measured $\pi$ pulse power ($817(16) \text{ nW}$). |
| Required Phononic Band Gap | $48$ | GHz | Target frequency for engineering environments. |
| Phononic Crystal Membrane Thickness | $60$ | nm | Required thickness for simulated $48 \text{ GHz}$ band gap structure. |
Key Methodologies
Section titled âKey MethodologiesâThe experimental achievement of coherent control in the $\text{SiV}^-$ center relies on a highly controlled MPCVD material growth followed by precision quantum optics techniques:
- Material Growth and Preparation: Experiments utilized high-purity diamond samples, including ion-implanted Type IIa HPHT diamond and homoepitaxially grown Silicon-doped CVD diamond on Type IIa HPHT substrates.
- Low-Temperature Optical Spectroscopy: Fluorescence spectra of the SiV ZPL were acquired at liquid helium temperatures ($5 \text{ K}$ to $150 \text{ K}$) to resolve the characteristic four-line fine structure caused by spin-orbit coupling and Zeeman interaction.
- Coherent Population Trapping (CPT): Continuous Wave (CW) lasers were applied to the ground state spin sublevels (D1 and D2 transitions) in a $\Lambda$-scheme under an external magnetic field ($0.73 \text{ T}$) to measure the spin coherence time ($\text{T}_2$).
- Microwave Control Implementation: Ground state spin manipulation was performed using Optically Detected Magnetic Resonance (ODMR) coupled with microwave pulses generated by simple loop antennas to drive Rabi oscillations.
- Ultrafast Optical Control: $12 \text{ ps}$ laser pulses were used for resonant optical excitation to drive rapid (up to $10\pi$ rotation) Rabi oscillations, demonstrating orbital state control in the picosecond regime.
- Strain/Phonon Engineering: Crystal strain was applied using Diamond Nano-Electro-Mechanical Systems (NEMS) components, increasing the SiV ground state splitting up to $470 \text{ GHz}$ to minimize phonon-driven decoherence.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and engineering services required to replicate this research, overcome current $\text{SiV}^-$ decoherence limitations, and scale QIP applications.
| Research Requirement | Material/Service Focus | 6CCVD Capability & Advantage |
|---|---|---|
| Ultra-High Purity Substrates | Low-defect, Type IIa quality material for maximal intrinsic coherence. | Optical Grade SCD Wafers: 6CCVD guarantees ultra-high purity, low-strain Single Crystal Diamond (SCD) material (up to $500 \text{ ”m}$ thickness) necessary to minimize parasitic defects (like residual nitrogen) that limit qubit performance. |
| Precision Silicon Doping | Controlled introduction of Si atoms during or after growth to create active $\text{SiV}^-$ centers. | Custom Doping via MPCVD: We offer precise, in-situ Silicon doping for both SCD and PCD wafers, providing superior control over Si concentration and integration compared to post-growth ion implantation methods, ensuring high-quality $\text{SiV}^-$ ensembles or single emitters. |
| Phononic Crystal Fabrication | Requirement for extremely thin, precise membranes ($60 \text{ nm}$ simulated) for band gap engineering. | Custom Thickness and Dimensions: 6CCVD supplies SCD and PCD wafers with thickness control from $0.1 \text{ ”m}$ up to $500 \text{ ”m}$, enabling researchers to create the thin diamond membranes critical for engineering phononic structures at the target $48 \text{ GHz}$ frequency. |
| NEMS and Microwave Components | Need for integrated electrodes and metal structures for strain and MW delivery. | Integrated Metalization Services: Our internal capabilities include precision deposition of Au, Ti, Pt, Pd, W, and Cu layers, ideal for creating high-quality microwave transmission lines, coplanar waveguides, and NEMS cantilever electrodes directly on the diamond substrate. |
| Optical Interface Quality | Need for surfaces with minimal scattering losses for high N.A. focusing of ultrafast lasers. | Atomic-Scale Polishing: We offer leading polishing services, achieving surface roughness $\text{Ra} < 1 \text{ nm}$ on SCD wafers and $\text{Ra} < 5 \text{ nm}$ on inch-size PCD, ensuring optimal photon collection and ultrafast optical pulse coupling. |
| Scalability & Dimension | Need for larger substrates to integrate multiple qubits (up to $125 \text{ mm}$ size mentioned in capabilities). | Large-Scale PCD Capability: While SiV work focuses on SCD, 6CCVD can supply PCD wafers up to $125 \text{ mm}$ for applications requiring large-area sensor or quantum component integration. |
6CCVDâs in-house PhD engineering team specializes in material selection and growth parameter optimization for advanced color center applications, including the Silicon Vacancy. We are prepared to assist researchers in selecting the ideal CVD diamond recipe (SCD or PCD, doping levels, growth axis) to maximize $\text{T}_2$ coherence times for scalable QIP systems.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Atomicâscale impurity spins, also called color centers, in an otherwise spinâfree diamond host lattice have proven to be versatile tools for applications in solidâstateâbased quantum technologies ranging from quantum information processing (QIP) to quantumâenhanced sensing and metrology. Due to its wide band gap, diamond can host hundreds of different color centers. However, their suitability for QIP or sensing applications has only been tested for a handful of these, with the nitrogen vacancy (NV) strongly dominating this field of research. Due to its limited optical properties, the success of the NV for QIP applications however strongly depends on the development of efficient photonic interfaces. In the past years the negatively charged silicon vacancy (SiV â ) center received significant attention due to its highly favourable spectral properties such as narrow zero phonon line transitions and weak phonon sidebands. Here, the recent work investigating the SiV centerâs orbital and electron spin coherence properties is reviewed as well as techniques to coherently control its quantum state using microwave as well as optical fields. Also, potential future experimental directions to improve the SiVâs coherence time scale and to develop it into a valuable tool for QIP applications are outlined.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2014 - Quantum Information Processing With Diamond