The Quantum Data Center: How we might actually scale quantum computing

Scalability and efficiency in quantum computing remains paramount, and Cisco’s vision is to build just such an infrastructure within a Quantum Data Center (QDC). Our latest exploration shares the architectural framework for distributed quantum computing, illustrating how this approach can unlock new possibilities and pave the way for future breakthroughs in quantum computing and networking technologies.

Pathway to scalable and useful quantum computing  

Quantum computing promises to tackle complex challenges that lie beyond the scope of classical systems but fully realizing its potential hinges on running millions of qubits. Today’s quantum computers, limited to only tens or hundreds of qubits, fall short of delivering the quantum advantage needed for real-world applications and use cases.

Cisco aims to bridge this gap with the concept of a Quantum Data Center—an environment where multiple quantum computers are networked together to form a distributed architecture that emulates the capabilities of a large-scale, monolithic quantum computer. We believe this practical approach can overcome the scaling limitations of individual quantum devices.

Cisco’s Quantum Data Center framework not only offers the scalability necessary for large-scale quantum computation but also provides the economic and operational benefits of centralized quantum resources in a controlled environment.

Cisco’s Quantum Data Center architecture 

Cisco is developing scalable architectures for quantum data center networks, drawing on foundational principles from classical data center networking—an area where we’re  already a proven leader. Our design uses a dynamic, circuit-switched quantum network to facilitate efficient entanglement distribution among quantum computers, leveraging shared resources such as measurement devices, quantum memories, and entanglement sources.

We’re currently evaluating several Quantum Data Center Network topologies, inspired by both switch-centric and server-centric designs common in today’s classical data centers. To support entanglement networking, our architecture incorporates three distinct protocols. This enables quantum computers to communicate via communication qubits equipped with spin-photon interfaces operating in either emitter, scatterer, or both modes.

We are also developing a network-aware Quantum Data Center orchestrator to manage the efficient execution of distributed quantum computing jobs to support multi-tenancy. By bridging the gap between physical-layer infrastructures and higher-level quantum applications, this orchestrator paves the way for seamless, large-scale and multi-tenant quantum operations. For those interested in a deeper dive, the technical details of Cisco’s Quantum Data Center design are outlined in our recent paper.

Cisco's network architecture for Quantum Data Center interconnect 

Cisco’s Quantum Data Center network is built around key principles to ensure a modular, scalable, and non-blocking quantum computing interconnect, leveraging an optical network fabric for entanglement distribution among quantum computers:

• Modular, on-demand connectivity: Our design employs a dynamic, circuit-switched network where entangled bits are generated by a limited set of shared resources—such as Bell state measurement devices, entanglement sources, and quantum memories—enabling efficient, all-to-all connectivity on demand.

• Classical data center-inspired topologies: We draw inspiration from established switch-centric and server-centric models used in classical data centers. This approach offers robust configurations for a range of quantum networking scenarios and scales.

• Versatile entangled bit generation protocols: Depending on the topology and distance requirements, our architecture supports three protocols—emitter-emitter, emitter-scatterer, and scatter-scatter—to facilitate reliable entanglement across the quantum data center network.

Network-aware Quantum Data Center orchestrator

A Quantum Data Center designed for distributed quantum computing requires an orchestration mechanism to manage and coordinate every layer of its architecture—from entangled bit generation at the physical layer to the execution of quantum applications. A key role of this orchestrator is to provide a framework for controlling quantum hardware and switches so that quantum computing tasks can be carried out in a distributed manner.

Our team has developed such an orchestration system. It accepts both a circuit-level description of quantum computing jobs and information about the Quantum Data Center topology (including the distribution of quantum hardware across the network). The orchestrator then outputs a set of instructions to configure the quantum interconnect, establishing end-to-end entanglement and enabling distributed quantum processing.

This orchestrator operates in two distinct phases:

• Circuit compilation: The quantum circuit is refined to meet physical-layer constraints, and logical qubits in the circuit are mapped to physical qubits in the data center’s quantum processors.
• Network scheduling: The orchestrator analyzes the compiled circuit and generates an optimized sequence of commands for configuring the entanglement distribution network. This ensures efficient remote gate operations and fully leverages available network resources.

Getting closer to the quantum advantage

The Cisco Quantum Research team is laying the groundwork for building large-scale quantum computing infrastructure, bringing us closer to practical quantum advantage. We have introduced novel Quantum Data Center network architectures that extend beyond traditional peer-to-peer approaches, unlocking multiple opportunities for future development. These architectures are complementary rather than mutually exclusive, allowing us to combine their strengths for greater impact. 

For technical details, please see  Quantum Data Center Infrastructures: A Scalable Architectural Design Perspective, and be sure to join us at our next virtual Cisco Quantum Summit to learn more about our latest efforts. 

In our next blog, we will go into more details about the network architecture needed for developing a large-scale quantum computing infrastructure.