Performance of Quantum Networks Using Heterogeneous Link Architectures

TL;DR

This paper investigates the performance of heterogeneous quantum networks built from Memory-Interference-Memory (MIM) and Memory-Source-Memory (MSM) link architectures using the QuISP simulator. It optimizes MSM operation by tuning the entangled photon pair source pulse rate and demonstrates that heterogeneity can be accommodated without a large drop in end-to-end Bell-pair generation, though performance strongly depends on link configuration and the slowest link. The study reveals a counterintuitive saturation effect where increasing EPPS pulse rate can reduce throughput, and shows that adaptive MSM can significantly improve long-distance performance, while on short links the benefit is limited. The results provide design guidance for scalable quantum internets, emphasizing robustness to heterogeneity and highlighting the importance of memory management and entanglement-swapping sequencing. A coarse empirical model is presented to capture the observed saturation behavior and end-to-end limitations, with code availability in the QuISP repository for reproducing and extending the analyses.

Abstract

The heterogeneity of quantum link architectures is an essential theme in designing quantum networks for technological interoperability and possibly performance optimization. However, the performance of heterogeneously connected quantum links has not yet been addressed. Here, we investigate the integration of two inherently different technologies, with one link where the photons flow from the nodes toward a device in the middle of the link, and a different link where pairs of photons flow from a device in the middle towards the nodes. We utilize the quantum internet simulator QuISP to conduct simulations. We first optimize the existing photon pair protocol for a single link by taking the pulse rate into account. Here, we find that increasing the pulse rate can actually decrease the overall performance. Using our optimized links, we demonstrate that heterogeneous networks actually work. Their performance is highly dependent on link configuration, but we observe no significant decrease in generation rate compared to homogeneous networks. This work provides insights into the phenomena we likely will observe when introducing technological heterogeneity into quantum networks, which is crucial for creating a scalable and robust quantum internetwork.

Figures (15)

• Figure 1: MIM link architecture. An external BSA is located between the two nodes. The two nodes emit photons from all available memories. The memories are then locked up until classical message response from the BSA is received. The classical message contains a list of BSM result, indicating the of success or failure, and the Pauli frame correction operations to apply to the memories upon success.
• Figure 2: MM link architecture with an internal BSA at one of the nodes. The basic protocol is generally the same for MIM links, but since the node on one side is equipped with the internal BSA, it can immediately decide whether to reset or keep a memory locked.
• Figure 3: MSM link architecture. An external EPPS (Entangled Photon Pair Source) is between the two nodes. The nodes actively make decisions regarding whether to retain or discard memories and what post-processing to apply in response to the measurement result or classical message they receive. The EPPS continues emitting photons at a fixed pulse rate, and each node independently counts incoming photon pairs, allowing individual partners to identify which photon pair their qubits are entangled with. If we successfully perform a local BSM, we retain the memory associated with the entangled photon and notify our partner node of the success on that photon pair, along with the corresponding Pauli frame. If we fail in a local BSM, we reset the memory and attempt again, sending a failure message to our partner. Additionally, when the memory is fully occupied, we disregard further incoming photons and notify our partner that the BSM has also failed for those photon pairs.
• Figure 4: The QuISP architecture of QNICs, QNodes (Quantum Networking Nodes), and quantum memories. Quantum memories can be set per QNIC. Here, the number of qubits is set to $\mathcal{N}$, and we can perform any single or multiple qubit gates within the quantum memories in the same node.
• Figure 5: Two hop networks where the link architectures are of various mixtures, which we simulated in experiment two.