Assessing the Role of Communication in Modular Multi-Core Quantum Systems

TL;DR

This work addresses the bottleneck that classical communication imposes on modular, cryogenically controlled multi-core quantum architectures. It introduces qcomm, an open-source simulator with a high-level timing model that jointly captures quantum gate execution, entanglement distribution, teleportation, and classical communication latency. Through extensive simulations on synthetic circuits and real benchmarks, the study shows that classical communication is not the dominant factor today but becomes increasingly impactful with larger networks, improved quantum technologies, or communication-aware circuit mappings, especially under optimized layouts. The findings inform architectural and compiler co-design for scalable modular quantum systems and point to future directions in MAC protocols, hybrid interconnects, and power-aware modeling to ensure practical scalability.

Abstract

The scalability of quantum computing is constrained by the physical and architectural limitations of monolithic quantum processors. Modular multi-core quantum architectures, which interconnect multiple quantum cores (QCs) via classical and quantum-coherent links, offer a promising alternative to address these challenges. However, transitioning to a modular architecture introduces communication overhead, where classical communication plays a crucial role in executing quantum algorithms by transmitting measurement outcomes and synchronizing operations across QCs. Understanding the impact of classical communication on execution time is therefore essential for optimizing system performance. In this work, we introduce \qcomm, an open-source simulator designed to evaluate the role of classical communication in modular quantum computing architectures. \qcomm{} provides a high-level execution and timing model that captures the interplay between quantum gate execution, entanglement distribution, teleportation protocols, and classical communication latency. We conduct an extensive experimental analysis to quantify the impact of classical communication bandwidth, interconnect types, and quantum circuit mapping strategies on overall execution time. Furthermore, we assess classical communication overhead when executing real quantum benchmarks mapped onto a cryogenically-controlled multi-core quantum system. Our results show that, while classical communication is generally not the dominant contributor to execution time, its impact becomes increasingly relevant in optimized scenarios -- such as improved quantum technology, large-scale interconnects, or communication-aware circuit mappings. These findings provide useful insights for the design of scalable modular quantum architectures and highlight the importance of evaluating classical communication as a performance-limiting factor in future systems.

Figures (39)

• Figure 1: Steps involved in teleportation protocol.
• Figure 2: Main modules of the proposed architecture.
• Figure 3: The address of a physical qubit is partitioned into the QC address and the local qubit address.
• Figure 4: From circuit to assembly code. Logical circuit (a). Compilation phase (b). Synthesized circuit (c). Assembly code (b).
• Figure 5: Format of the instruction bundle.