NetSquid, a NETwork Simulator for QUantum Information using Discrete events
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-07-16 |
| Journal | Communications Physics |
| Authors | Tim Coopmans, Robert Knegjens, Axel Dahlberg, David Maier, Loek Nijsten |
| Institutions | QuTech, SURFsara (Netherlands) |
| Citations | 187 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: NetSquid Quantum Network Simulation
Section titled âTechnical Documentation & Analysis: NetSquid Quantum Network SimulationâSource Paper: Coopmans et al., âNetSquid, a NETwork Simulator for Quantum Information using Discrete events,â Communications Physics (2021).
Executive Summary
Section titled âExecutive SummaryâThis research introduces NetSquid, a modular, discrete-event simulator for analyzing the performance and requirements of scalable quantum networks, with a strong focus on physical layer non-idealities. The findings directly validate the critical need for high-specification MPCVD diamond materials.
- Application Validation: NetSquid successfully models quantum repeater chains based on Nitrogen-Vacancy (NV) centers in diamond and atomic ensembles (AFC/EIT), simulating entanglement distribution over distances up to 1500 km.
- Material Criticality: The simulation confirms that physical layer parametersâspecifically two-qubit gate fidelity (FEC) and photon detection probability (Pdet)âare the most sensitive factors determining end-to-end entanglement fidelity.
- Performance Benchmarks: Achieving entanglement fidelity above the classical threshold (F > 0.5) requires hardware performance improvements (e.g., 10x to 50x) over near-term estimates, necessitating ultra-high-quality diamond substrates.
- Scalability Demonstrated: The simulatorâs design allows for the analysis of large networks, modeling entanglement distribution over chains of up to one thousand nodes.
- 6CCVD Value Proposition: 6CCVD specializes in providing the ultra-low strain, high-purity Single Crystal Diamond (SCD) required to fabricate NV centers capable of achieving the long coherence times (T1, T2) and high gate fidelities necessary for practical quantum repeaters.
- Engineering Requirement: The research underscores that the physical material properties of the diamond substrate are the fundamental bottleneck for scaling quantum networks.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the simulation results concerning NV-based quantum repeater chains and memory performance:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Simulated Distance | 1500 | km | Repeater chain analysis. |
| Classical Fidelity Threshold | 0.5 | Dimensionless | Minimum fidelity required for successful entanglement. |
| Near-Term Two-Qubit Gate Fidelity (FEC) | 0.985 | Dimensionless | Baseline NV hardware estimate. |
| 3x Improved Two-Qubit Gate Fidelity (FEC) | 0.997 | Dimensionless | Required to boost fidelity beyond 0.5. |
| Near-Term Detection Probability (Pdet) | 6.8 | % | Baseline NV hardware estimate. |
| 3x Improved Detection Probability (Pdet) | 58 | % | Required to boost fidelity beyond 0.5. |
| Near-Term Visibility (V) | 95 | % | Baseline NV hardware estimate. |
| 3x Improved Visibility (V) | 99 | % | Baseline NV hardware estimate. |
| Memory Coherence Time (T2) | Up to 10 | ”s | Quantum switch analysis with memory dephasing noise. |
| Optimal Repeater Configuration | 3 or 7 | Nodes | Outperforms no-repeater setup beyond 750 km (10x improved hardware). |
Key Methodologies
Section titled âKey MethodologiesâThe simulation utilized a highly modular, discrete-event approach to accurately model the complex interplay between physical hardware and control protocols.
- Discrete-Event Simulation Engine: NetSquid employs the PyDynAA C++ engine to manage an asynchronous timeline, advancing time by stepping from event to event (e.g., qubit arrival, measurement, classical message exchange). This allows for accurate tracking of time-dependent noise (decoherence).
- Modular Component Modeling: All physical devices (NV centers, quantum memories, optical fibers, channels) are represented as modular components, enabling rapid substitution of hardware platforms (e.g., switching from NV centers to AFC/EIT memories).
- NV Center Physical Model: NV centers were modeled as a quantum processor containing a communication qubit (electronic spin-1) and multiple storage qubits (13C nuclear spins) connected in a star topology.
- Decoherence and Noise Implementation: Noise was modeled using exponential T1 and T2 relaxation times for both electron and nuclear spins. Quantum gates were modeled as noisy operations (Onoisy) followed by a depolarizing channel (Ndepol).
- Entanglement Generation Simulation: Remote entanglement generation between adjacent NV nodes was simulated using a model based on single-photon detection and probabilistic success, incorporating photon travel delay and midpoint heralding delay.
- Protocol Benchmarking: Two primary repeater protocols were analyzed: SWAP-ASAP (immediate swapping) and NESTED-WITH-DISTILL (nested protocol with entanglement purification).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe NetSquid simulation results clearly define the stringent material requirements necessary for realizing high-performance quantum repeaters. 6CCVD is uniquely positioned to supply the foundational MPCVD diamond materials and engineering services required to meet these demands.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate and extend the â10x improvedâ hardware performance simulated in this research, researchers require diamond substrates optimized for long coherence times and minimal noise.
- Optical Grade Single Crystal Diamond (SCD):
- Requirement: Essential for NV center fabrication. The material must be ultra-high purity (low [N] and [B] concentrations) and low-strain to maximize the T1 and T2 coherence times of the NV electronic and nuclear spins, which are critical parameters in the simulation.
- 6CCVD Offering: We provide high-quality MPCVD SCD wafers specifically grown for quantum applications, ensuring the material integrity needed for long-lived quantum memories.
- Boron-Doped Diamond (BDD):
- Requirement: While not the primary material for NV centers, BDD is crucial for high-performance electrochemical and sensing applications in related quantum architectures.
- 6CCVD Offering: We supply custom-doped BDD films for specialized device integration.
Customization Potential
Section titled âCustomization PotentialâThe integration of NV centers into functional quantum processors demands precise control over geometry, surface quality, and electrical contacts.
| Requirement from Research | 6CCVD Customization Capability | Technical Specification |
|---|---|---|
| Minimizing Storage Qubit Noise | Ultra-smooth surface finishing is required to reduce surface-induced decoherence. | Polishing: Ra < 1 nm (SCD) guaranteed. |
| Optimizing Optical Coupling | Precise control over SCD thickness is necessary for optimal NV depth and integration with solid immersion lenses (SILs). | Thickness: SCD plates available from 0.1 ”m up to 500 ”m. |
| Device Integration & Control | Custom metal contacts are often needed for microwave/RF control and readout of the NV spins. | Metalization: In-house deposition of Au, Pt, Pd, Ti, W, and Cu films. |
| Modular Architectures | Future large-scale systems may require large-area substrates for integration. | Custom Dimensions: PCD wafers up to 125 mm diameter. |
| Substrate Handling | NV fabrication often requires thick, robust handling layers. | Substrates: Available up to 10 mm thickness. |
Engineering Support
Section titled âEngineering SupportâThe NetSquid simulation demonstrated that achieving high fidelity (F > 0.5) is highly sensitive to detection probability and two-qubit gate noise. Optimizing these parameters requires deep expertise in diamond growth and processing.
- Material Optimization: 6CCVDâs in-house PhD team can assist researchers in tailoring MPCVD growth recipes (e.g., gas ratios, temperature, pressure) to minimize impurities and lattice defects, directly improving the T1 and T2 times of the NV centers and boosting gate fidelity.
- Process Integration: We offer consultation on material selection and post-processing techniques (e.g., surface termination, etching) to ensure compatibility with downstream NV implantation and device fabrication processes.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract In order to bring quantum networks into the real world, we would like to determine the requirements of quantum network protocols including the underlying quantum hardware. Because detailed architecture proposals are generally too complex for mathematical analysis, it is natural to employ numerical simulation. Here we introduce NetSquid, the NETwork Simulator for QUantum Information using Discrete events, a discrete-event based platform for simulating all aspects of quantum networks and modular quantum computing systems, ranging from the physical layer and its control plane up to the application level. We study several use cases to showcase NetSquidâs power, including detailed physical layer simulations of repeater chains based on nitrogen vacancy centres in diamond as well as atomic ensembles. We also study the control plane of a quantum switch beyond its analytically known regime, and showcase NetSquidâs ability to investigate large networks by simulating entanglement distribution over a chain of up to one thousand nodes.