Quantum Networks: Faster Entanglement Boosts Security

Distributing entanglement to multiple parties is a crucial step towards building a quantum internet, but current methods demand significant resources to store the entangled pairs until distribution is complete. Luise Prielinger from QuTech, Delft University of Technology, and Kenneth Goodenough, Guus Avis, et al. from the University of Massachusetts, now present a new protocol, termed ‘Piecemaker’, that dramatically reduces this storage burden. Their approach processes entangled pairs immediately upon creation, rather than waiting to establish all connections before distribution, thereby minimising cumulative noise and improving fidelity. The team demonstrates, through detailed simulations, that Piecemaker consistently achieves equal or higher fidelity in distributed states, with reductions in infidelity reaching up to 45%, and expands the range of conditions under which reliable multipartite entanglement can be established.

End users represent a key consideration in quantum communication protocols. Existing schemes typically begin by generating entangled pairs between a central switch and each user, often requiring complete establishment of all connections before distributing the desired quantum state via measurement. This research takes a different approach, storing only a minimal subset of entangled pairs and processing each one immediately upon creation. By reducing the time entangled pairs are stored, the protocols minimize cumulative noise, a significant advantage over conventional methods. The protocol design is theoretically grounded in the structure of vertex covers within graph states, a mathematical representation of entanglement.

Quantum Networking and Entanglement Distribution References

This is a comprehensive list of references detailing research focused on quantum networking, entanglement distribution, and related topics. The collection covers several core themes and research areas, including building quantum networks, long-distance entanglement distribution, and quantum repeaters. Research also focuses on creating and sharing entangled states, and improving entanglement quality through distillation. Graph states are a powerful way to represent and manipulate entanglement, connecting them to Clifford groups important for quantum error correction, a driving force behind much of the research.

References detail experimental implementations using various physical systems, such as solid-state qubits and photons, and optimization of resource use to achieve the best performance. Key researchers in this field include Avis and Wehner, who focus on network architecture and optimization; Coopmans and Elkouss, who specialize in quantum repeater design; and Dahlberg, Helsen, and Wehner, who are experts in graph states and their manipulation. Elkouss and collaborators, such as de Bone and Jansen, are leading researchers in entanglement distillation, while Hanson and collaborators are building and demonstrating quantum network components. Nielsen and Chuang provide the foundational theory in their standard textbook on quantum computation.

The bibliography covers specific topics in detail, including entanglement swapping, Bell state measurement, quantum key distribution, quantum teleportation, cut-off optimization, symmetry reduction, and various distillation protocols. In conclusion, this bibliography represents a comprehensive overview of the current state of research in quantum networking and related fields, highlighting the challenges and opportunities in building a quantum internet and the ongoing efforts to develop the necessary technologies and protocols. The sheer number of references indicates the rapid growth and complexity of this exciting field.

Fast Multipartite Entanglement Distribution via Fusion

Researchers have developed new protocols for distributing multipartite entanglement, a crucial resource for quantum technologies, that significantly improve upon existing methods. These protocols focus on efficiently distributing entangled states from a central switch to multiple remote end users, minimizing the time entangled pairs are stored and therefore reducing accumulated noise. The core innovation lies in processing incoming entangled pairs immediately, rather than waiting to establish all connections before distributing the final state, an approach grounded in the mathematical structure of graph states and utilizing a technique akin to piece-wise fusion. Through comprehensive numerical simulations, the team compared their protocols to a standard “Factory” protocol, where the switch creates the entire entangled state before distributing it.

The results demonstrate that the new protocols consistently achieve equal or higher fidelity, and can reduce errors by up to 45%. Importantly, the new protocols maintain a critical fidelity threshold across a wider range of conditions, including lower success rates for establishing entangled links and higher levels of noise, showing a clear advantage in simulations involving up to 50 interconnected qubits, particularly in challenging environments. The improvement stems from reducing the storage time of fragile entangled pairs, susceptible to degradation from environmental noise. The researchers tested these protocols with various network configurations, including linear and grid-shaped networks, finding consistent improvements over the Factory protocol, suggesting the new approach is robust and adaptable. While the study did not focus on the speed of state distribution, the protocols are compatible with existing rates achieved by the Factory protocol, meaning improvements in fidelity do not come at the cost of slower communication. These advancements represent a significant step towards building practical and reliable quantum networks for secure communication and distributed quantum computing.

Piecemaker Protocols Enhance Multipartite Entanglement Distribution

This research introduces new protocols for distributing multipartite entanglement using a quantum switch, achieving improvements over existing methods. The protocols, termed ‘Piecemaker’, focus on efficiently distributing both GHZ states and more general stabilizer states to multiple end users. By strategically managing the storage of entangled pairs, the switch minimizes cumulative noise and enhances the fidelity of the distributed states, with the GHZ Piecemaker demonstrating the largest fidelity improvement. The team demonstrates that these protocols consistently achieve equal or higher fidelity compared to previous approaches, reducing infidelity by up to 45% in some cases.

Notably, the GHZ Piecemaker proves less susceptible to variations in link lengths between the switch and end nodes. The success of the general Piecemaker relies on the concept of LC equivalence, which allows the switch to reduce memory requirements by storing fewer entangled pairs. While these protocols represent a significant step forward, the authors acknowledge they operate under simplified assumptions and form an initial contribution to understanding stabilizer state distribution. Future work will focus on refining the protocols and evaluating their performance under more realistic hardware constraints, potentially including limitations such as cutoff times for storing entangled pairs.