Entanglement distribution between quantum repeater nodes with an absorptive type memory
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-08-01 |
| Journal | International Journal of Quantum Information |
| Authors | Daisuke Yoshida, Kazuya Niizeki, Shuhei Tamura, Tomoyuki Horikiri |
| Institutions | Yokohama National University, Japan Science and Technology Agency |
| Citations | 6 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Rate Entanglement Distribution via AFC Quantum Memory
Section titled âTechnical Documentation & Analysis: High-Rate Entanglement Distribution via AFC Quantum MemoryâExecutive Summary
Section titled âExecutive SummaryâThis analysis focuses on the proposed entanglement distribution scheme utilizing an Atomic Frequency Comb (AFC) absorptive quantum memory, demonstrating a significant advancement in quantum repeater technology.
- Core Achievement: The AFC scheme achieves an entanglement distribution rate nearly two orders of magnitude higher than previously studied spin-photon entanglement memories (e.g., Diamond NV centers, Quantum Dots, Trapped Ions).
- Mechanism: The improvement stems from the AFCâs ability to enable temporal multimode operation using a single crystal (Rare-Earth Ion Doped Solid, REIDS), overcoming the difficulty of scaling multiple memories.
- Key Performance Metric: Optimistic simulations show potential entanglement distribution rates approaching 1 MHz at 50 km link distances when using high-mode-number materials like Tm:YAG ($N_{AFC} = 1060$) and perfect absorption ($P_{AFC} = 1$).
- Feasibility: The protocol uses state-of-the-art technology, including non-destructive photon detectors (nDPDs) and high-efficiency AFC absorption/reemission (up to 53% demonstrated, 100% in principle).
- 6CCVD Relevance: While the AFC uses REIDS, the research directly compares performance against Diamond NV centers. 6CCVD provides the high-purity Single Crystal Diamond (SCD) substrates necessary for both advanced NV research and as superior thermal/optical platforms for REIDS integration.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters were extracted from the simulation and comparison data presented in the research paper.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optical Fiber Attenuation Length ($L_{att}$) | 22 | km | Standard telecommunication fiber |
| Speed of Light ($c$) | $2.998 \times 10^{5}$ | km/s | Speed of light in vacuum |
| Optical Fiber Refractive Index ($n$) | 1.5 | - | Used for calculating $t_{link}$ |
| SPD Efficiency ($p_d$) | 0.8 | - | Single Photon Detector efficiency |
| AFC Rephasing Time ($2\pi/\Delta$) | 51 | ”s | Based on Eu:YSO REIDS |
| AFC Coherent Time | 1 | ms | Sufficient for quantum repeater operation |
| AFC Number of Modes ($N_{AFC}$) | 100 | - | Used in realistic simulation |
| AFC Number of Modes (Optimistic) | 1060 | - | Demonstrated in Tm:YAG REIDS |
| AFC Absorption Efficiency ($P_{AFC}$) | 0.53 | - | Pessimistic/Realistic value |
| Clock Time ($t_{clock}$) | 10 | ns | Used for QD and AFC simulations |
| Diamond NV Center Cycle Time | 100 | ns | Comparison material (Table I) |
| Diamond NV Center Emission Fraction | 0.50 | - | Comparison material (Table I) |
Key Methodologies
Section titled âKey MethodologiesâThe entanglement distribution rate analysis relied on numerical simulations of the Atomic Frequency Comb (AFC) protocol using two primary quantum communication schemes: Meet-in-the-Middle (MM) and Midpoint Source (MS).
- Material Selection: Rare-Earth Ion Doped Solids (REIDS), such as Eu:YSO and Tm:YAG, were assumed as the memory material for the AFC protocol due to their temporal multiplexing capability.
- AFC Implementation: The AFC structure is created using a hole-burning technique with an intense laser, generating absorption lines with interval $\Delta$ within a wide inhomogeneous broadening range.
- Protocol Schemes:
- AFC-MM: Entangled Photon Sources (EPS) are placed near the memory in the repeater nodes, and a Bell State Analyzer (BSA) is placed at the midpoint.
- AFC-MS: The EPS is placed at the midpoint, and the repeater nodes utilize non-destructive photon detectors (nDPDs) before the AFC memory to provide a weak heralding signal.
- Simulation Parameters: The Monte Carlo method was used to calculate the average entanglement distribution rate over $5 \times 10^{5}$ synchronization time rounds ($t_{round}$).
- Optimistic Scenario: The highest rates were achieved assuming $N_{AFC} = 1060$ (based on Tm:YAG) and perfect absorption ($P_{AFC} = 1$), demonstrating rates up to $10^{6}$ $s^{-1}$ at 50 km.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to support both the foundational research compared in this paper (NV centers) and the advanced engineering required to implement the high-rate AFC quantum repeater platforms.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Material Solution | Technical Specification |
|---|---|---|
| NV Center Comparison | Optical Grade Single Crystal Diamond (SCD) | High-purity, low-strain substrates for creating and studying high-fidelity NV centers. |
| AFC Platform Integration | Polycrystalline Diamond (PCD) Plates | Wafers up to 125mm diameter for stable, large-area optical benches and superior thermal management for REIDS crystals (Eu:YSO, Tm:YAG). |
| High-Efficiency Optics | Optical Grade SCD | Polishing to Ra < 1nm for critical interfaces, ensuring minimal scattering loss when coupling photons into the memory or fiber. |
| Non-Destructive Detectors (nDPD) | Boron-Doped Diamond (BDD) | Custom BDD films for potential integration into detector or control circuitry, leveraging diamondâs unique electrical and thermal properties. |
Customization Potential
Section titled âCustomization PotentialâThe implementation of high-rate quantum repeaters requires precise, integrated components (BSAs, nDPDs, memory coupling). 6CCVD offers specialized services critical for moving this research from simulation to deployment:
- Custom Dimensions: We provide diamond plates and wafers in custom shapes and sizes, including PCD wafers up to 125mm, necessary for large-scale optical setups supporting the AFC memory.
- Precision Polishing: Our internal capability ensures SCD surfaces achieve roughness (Ra) below 1nm, essential for minimizing optical loss at the memory interface ($P_{optical}$).
- Advanced Metalization: We offer in-house deposition of standard and custom metal stacks (Au, Pt, Pd, Ti, W, Cu). This is vital for integrating control electrodes, thermal contacts, or custom circuitry onto diamond heat sinks for nDPDs and REIDS cooling.
- Thickness Control: We supply SCD and PCD films with precise thickness control, ranging from 0.1”m to 500”m, allowing researchers to optimize optical depth and thermal performance.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers specializes in optimizing MPCVD diamond for quantum applications. We offer consultation services to assist researchers in:
- Thermal Management: Designing diamond heat spreaders to manage the heat load from intense control lasers used in the AFC hole-burning technique.
- Material Selection: Advising on the optimal diamond grade (SCD vs. PCD) and surface preparation for mounting or integrating Rare-Earth Ion Doped Solids (REIDS) for similar Quantum Memory and Repeater projects.
- Custom NV Doping: Providing tailored NV-doped SCD substrates for researchers continuing comparative studies against the high-performance AFC protocol.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Quantum repeaters, which are indispensable for long-distance quantum communication, are necessary for extending the entanglement from short distance to long distance; however, high-rate entanglement distribution, even between adjacent repeater nodes, has not been realized. In a recent work by [C. Jones et al., New J. Phys. 18 (2016) 083015], the entanglement distribution rate between adjacent repeater nodes was calculated for a plurality of quantum dots, nitrogen-vacancy centers in diamond, and trapped ions adopted as quantum memories inside the repeater nodes. Considering practical use, arranging a plurality of quantum memories becomes so difficult with the state-of-the art technology. It is desirable that high-rate entanglement distribution is realized with as few memory crystals as possible. Here, we propose new entanglement distribution scheme with one quantum memory based on the atomic frequency comb which enables temporal multimode operation with one crystal. The adopted absorptive-type quantum memory degrades the difficulty of multimode operation compared with the previously investigated quantum memories directly generating spin-photon entanglement. It is shown that this scheme improves the distribution rate by nearly two orders of magnitude compared with the result in [C. Jones et al., New J. Phys. 18 (2016) 083015] and the experimental implementation is close by utilizing state-of-the-art technology.