Concurrent Quantum Strategies

Binjie He, Seng W. Loke, Luke Lu +1 more

Entanglement swapping is a crucial step in quantum communication, generating long-distance entanglements between quantum users for quantum network applications, such as distributed quantum computing. This study focuses on the efficiency of entanglement swapping strategies in quantum networks, particularly in multi-user concurrent quantum communication. Since multi-user concurrent quantum communication consists of multiple point-to-point quantum communications, we first analyze the challenges faced by existing entanglement swapping strategies in this scenario and then propose Parallel Segment Entanglement Swapping (PSES) to address them. PSES utilizes a tree-like model to divide the path into segments and execute entanglement swapping in parallel across them, thereby enhancing the generation rate of long-distance entanglement. Furthermore, we analyze the impact of resource contention on entanglement swapping in multi-user concurrent quantum communication and propose Multi-user PSES (M-PSES) to alleviate this negative impact. M-PSES leverages the entanglement swapping trigger signal and resource locking mechanisms to mitigate resource contention. The simulation results show that PSES performs superiorly to existing entanglement swapping strategies in point-to-point quantum communication, and M-PSES can achieve better performance than PSES in multi-user concurrent quantum communication.

Prateek Tandon, Stanley Lam, Ben Shih +3 more

Juan Fernández‐Herrerín‐Álvarez, Francisco Javier González-Castaño, Ana Fernández Vilas

ABSTRACT Quantum networks rely on entanglement distribution to enable secure communication and distributed quantum computation. Most analytical models address idealized, single‐flow scenarios and overlook the impact of concurrent entanglement requests, limiting their applicability to realistic network conditions. This work studies the behavior of a quantum switch under simultaneous entanglement demands, motivated by the need to understand how concurrency affects link utilization, generation rate, and end‐to‐end fidelity. Our main contribution is a concurrency‐aware switch model that jointly captures capacity and fidelity under multi‐flow conditions, offering the first systematic simulation‐based analysis of this problem. Results show that handling several requests at the same time improves throughput but reduces fidelity once the network is too busy. This highlights the need for scheduling and routing strategies that keep a good balance between efficiency and entanglement quality in future quantum networks.

Jianchuan Tan, An Min Wang

Canh Minh Do, Tsubasa Takagi, Kazuhiro Ogata

While constructing practical quantum computers by big companies remains a challenge, the application of quantum communication and cryptography has made remarkable progress. Therefore, it is crucial to verify quantum protocols before they can be trusted in safety and security-critical applications. We have proposed Basic Dynamic Quantum Logic (BDQL) to formalize and verify sequential models of quantum protocols with a support tool developed in Maude. However, BDQL does not support concurrency in its formalization. This article introduces Concurrent Dynamic Quantum Logic (CDQL), an extension of BDQL, to formalize and verify concurrent models of quantum protocols. CDQL is more expressive than BDQL by considering concurrent behavior and communication among participants in quantum protocols. Since CDQL is a conservative extension of BDQL, we extend the syntax of BDQL to CDQL and make a transformation from CDQL to BDQL without interrupting the semantics of BDQL. We also extend the implementation of BDQL to support CDQL, making a new support tool in Maude. The new support tool is equipped with a lazy rewriting strategy to make the verification process significantly faster. Several quantum communication protocols are successfully formalized and verified in BDQL/CDQL, demonstrating the effectiveness of our automated approach and tool in verifying quantum protocols.

Mingsheng Ying