Multidimensional cluster states using a single spin-photon interface coupled strongly to an intrinsic nuclear register
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-10-19 |
| Journal | Quantum |
| Authors | Cathryn P. Michaels, JesĂșs Arjona MartĂnez, Romain Debroux, Ryan A. Parker, Alexander M. Stramma |
| Institutions | University of Cambridge |
| Citations | 28 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Multidimensional Cluster States in Diamond
Section titled âTechnical Documentation & Analysis: Multidimensional Cluster States in DiamondâThis document analyzes the research paper âMultidimensional cluster states using a single spin-photon interface coupled strongly to an intrinsic nuclear registerâ and outlines how 6CCVDâs advanced MPCVD diamond materials and processing capabilities directly support the replication and extension of this critical quantum computing research.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Proposal and numerical demonstration of generating multidimensional photonic cluster states (up to 2x50 photons) using a single, efficient spin-photon interface.
- Material Platform: The scheme identifies the Silicon-29 Vacancy (29SiV) center in high-purity diamond, coupled to a nanophotonic structure, as the optimal solid-state platform.
- Mechanism: Entanglement is generated via a strong hyperfine link between the electronic proxy qubit (SiV spin) and an intrinsic nuclear register (29Si nucleus).
- Performance Metrics: Current experimental parameters allow for a 2x5 cluster state with a lower-bound fidelity F > 0.5 and a high repetition rate of 65 kHz.
- Future Potential: With realistic gate improvements and long electronic coherence times (T2 ~ 300 ”s), the scheme projects generating 100-photon (2x50) cluster states with fidelity F > 0.9.
- Material Requirements: Success hinges on ultra-low-strain, high-purity Single Crystal Diamond (SCD) substrates capable of hosting high-coherence SiV centers and supporting high-efficiency nanophotonic integration (e.g., nanocavities).
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key performance parameters and material requirements extracted from the analysis of the SiV-based cluster state generation protocol.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Cluster State Size (Achievable) | 2x5 (10 photons) | N/A | Based on current experimental performance |
| Target Cluster State Size (Projected) | 2x50 (100 photons) | N/A | Requires improved gate fidelity (F > 0.9) |
| Cluster State Fidelity (F) | > 0.5 | N/A | Lower bound for 2x5 state |
| Cluster State Repetition Rate (R) | 65 | kHz | For 2x5 state (3 ”s scheme length) |
| SiV Electronic Coherence Time (T2) | 10 | ms | Dynamically decoupled (at 100 mK) |
| SiV Hyperfine Constant (A||) | 70 | MHz | Isotropic coupling to 29Si nucleus |
| Magnetic Field (B) | 0.6 | T | Selected for fast gate operation |
| SWAP Gate Duration | 1.6 | ”s | Calculated duration for electron-nuclear gate |
| CZ Gate Duration | 1.1 | ”s | Calculated duration for electron-nuclear gate |
| System Detection Efficiency (ηCE) | 85 | % | Achieved via nanophotonic coupling |
| Cavity Cooperativity (C) | 105 ± 11 | N/A | Required for Purcell enhancement |
| SiV Excited State Lifetime (Ï) | 1.6 | ns | Used in simulation |
Key Methodologies
Section titled âKey MethodologiesâThe protocol relies on a deterministic quantum circuit executed on a single SiV center coupled to its intrinsic 29Si nuclear spin register, integrated within a nanophotonic structure.
- Material Selection: Identification of Group IV color centers in diamond (specifically SiV) due to their inversion symmetry, reduced sensitivity to electric field fluctuations, and compatibility with nanophotonic structures.
- Initialisation & Preparation: Proxy qubit (SiV electron spin) and nuclear qubits (29Si) are initialized to the |0> state, followed by Ry(Ï/2) rotations to create superposition states.
- Qubit Entanglement: Hyperfine-enabled Controlled-Phase (CZ) gates are applied sequentially between the proxy qubit and the nuclear register. Gate speed is limited by the hyperfine interaction strength (A|| = 70 MHz).
- Photon Emission: The proxy qubit generates sequential photon qubits, entangled with the proxy spin state, typically via SWAP gates and cyclic optical transitions. Polarization encoding is preferred to minimize dephasing errors.
- Nanophotonic Integration: The SiV center must be coupled to a high-cooperativity (C > 100) nanocavity or waveguide to achieve high photon collection efficiency (ηCE up to 85%) and Purcell enhancement.
- Gate Optimization: Electron-nuclear gates (SWAP, CZ) are constructed using dynamically decoupled pulse sequences, optimized numerically to achieve high fidelity (> 99.9%) while minimizing decoherence effects (T2).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical role of high-quality MPCVD diamond in achieving scalable quantum computation. 6CCVD is uniquely positioned to supply the foundational materials and custom processing required to realize and advance this SiV-based cluster state generation scheme.
Applicable Materials
Section titled âApplicable MaterialsâThe success of this protocol is fundamentally dependent on the quality of the diamond host material, particularly its purity, strain, and defect control.
| Research Requirement | 6CCVD Solution & Material Recommendation | Technical Advantage |
|---|---|---|
| High-Coherence SiV Host | Optical Grade Single Crystal Diamond (SCD) | Ultra-low nitrogen and strain levels, essential for achieving the long electronic coherence times (T2 > 10 ms) required for high-fidelity gates. |
| Nanophotonic Integration | Custom Thin SCD Plates (0.1 ”m - 500 ”m) | Thin membranes are necessary for fabricating high-Q nanocavities and waveguides (e.g., along the SiVâs (111) symmetry axis). 6CCVD provides custom thickness control up to 500 ”m. |
| Intrinsic Nuclear Register | High-Purity SCD Substrates | While 29Si is intrinsic, the overall low-defect density of 6CCVD SCD minimizes background nuclear spin noise (e.g., 13C), which limits T2 and gate fidelity. |
Customization Potential
Section titled âCustomization PotentialâReplicating and extending this research requires precise material engineering beyond standard wafers. 6CCVD offers comprehensive customization services:
- Custom Dimensions: We provide SCD plates and wafers in custom sizes, enabling large-scale integration of nanophotonic circuits. Our PCD capability extends up to 125mm diameter, suitable for high-throughput processing development.
- Precision Polishing: Achieving high-Q nanocavities and low-loss waveguides demands exceptional surface quality. 6CCVD guarantees Ra < 1 nm polishing for SCD, ensuring minimal scattering losses critical for the required 85% photon collection efficiency (ηCE).
- Metalization Services: The protocol requires precise control (e.g., microwave pulses for electron control, external magnetic fields). 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for creating on-chip microwave antennas and electrical contacts necessary for gate operation and readout.
- Substrate Thickness Control: We offer substrates up to 10 mm thick for robust mounting, or thin SCD membranes (down to 0.1 ”m) necessary for lift-off and integration into complex nanophotonic architectures.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in MPCVD growth optimization for quantum applications. We offer consultation services to assist researchers in selecting the optimal diamond specifications (purity, orientation, and surface termination) for similar Group IV Color Center Quantum Computing projects. We ensure the starting material is optimized for subsequent SiV creation (via implantation or in-situ growth) and nanophotonic fabrication.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Photonic cluster states are a powerful resource for measurement-based quantum computing and loss-tolerant quantum communication. Proposals to generate multi-dimensional lattice cluster states have identified coupled spin-photon interfaces, spin-ancilla systems, and optical feedback mechanisms as potential schemes. Following these, we propose the generation of multi-dimensional lattice cluster states using a single, efficient spin-photon interface coupled strongly to a nuclear register. Our scheme makes use of the contact hyperfine interaction to enable universal quantum gates between the interface spin and a local nuclear register and funnels the resulting entanglement to photons via the spin-photon interface. Among several quantum emitters, we identify the silicon-29 vacancy centre in diamond, coupled to a nanophotonic structure, as possessing the right combination of optical quality and spin coherence for this scheme. We show numerically that using this system a 2Ă5-sized cluster state with a lower-bound fidelity of 0.5 and repetition rate of 65 kHz is achievable under currently realised experimental performances and with feasible technical overhead. Realistic gate improvements put 100-photon cluster states within experimental reach.