Universal Nested Quantum Switch

TL;DR

This paper introduces a scalable, resilient quantum network construction that distributes entanglement efficiently without relying on a central node, improving over previous methods in resource scaling.

Contribution

It presents a novel nested quantum switch architecture with logarithmic qubit and Bell pair scaling, enhancing distributed quantum network capabilities.

Findings

Achieves logarithmic qubits per node with $O(n\,log n)$ Bell pairs.

Provides a flexible, fully connected pairwise quantum network.

Introduces a graph state variant with minimal qubits per node.

Abstract

The quantum switch is a basic network primitive that allows one to connect multiple nodes in a quantum network via a central node. We show that the same functionality can be achieved with a different geometry that does not rely on a powerful and large central unit, but instead utilizes evenly distributed resources. This approach is resilient against node failures. We provide a nested construction with logarithmically many qubits per node and a total of $O(n\log n)$ Bell pairs, in contrast to other distributed approaches based on pre-shared entanglement that scale as $O(n^2)$. The construction achieves fully flexible pairwise connectivity, where the shared resource state can be locally transformed into $n/2$ arbitrarily distributed Bell states. We also present a graph state variant with just one qubit per node, which allows one to generate $O(n/\log^2 n)$ Bell pairs.