Cisco shared details about its prototype Quantum Network Controller along with an updated release of its Network-Aware Quantum Compiler for networking distributed quantum environments.
Cisco continues to fill out its portfolio of quantum network technology, this week adding a core control mechanism for distributed quantum networks.
Cisco’s prototype Quantum Network Controller is designed to coordinate all components of a quantum network—including quantum computers, quantum memories, and quantum switches—and make them usable on one network, without an application having to understand how every piece works, according to a blog post about the news from Vijoy Pandey, senior vice president and general manager of Outshift by Cisco.
“Until now, quantum networks have been built point to point, one link at a time, which kept them to a handful of nodes. At that size, running them with hand-built software was painful but workable,” Pandey wrote.
“Connecting 1,000 quantum nodes point to point takes close to 500,000 dedicated links. The switch is designed to let every node reach every other node over one shared fabric instead,” Pandey wrote. “Once that fabric scales, deciding who gets entanglement, at what quality, in what order, with what guarantees and on what timing isn’t a human-scale task. It takes software coordinating every device with the timing precision quantum operations demand. The Controller is that coordinator.”
“The Controller exposes an interface for each device category—sources, switches, detectors, and timing systems—with a hardware abstraction layer (HAL) underneath, so any vendor’s hardware in that category plugs in the same way,” he wrote. “An application requests entanglement, naming the endpoints, rate, fidelity, and timing it needs, without knowing how any of that gets physically produced. We call the model Entanglement-as-a-Service (EaaS). It does for entanglement what shared cloud infrastructure did for CPU cycles, turning a resource that used to require a dedicated physical connection into something the network schedules on demand.”
Pandey added: “Because the information in a quantum state cannot be read without destroying it, the Controller cannot inspect traffic the way a classical monitoring tool would. Instead, it verifies link quality statistically, applies predefined tuning, retry, or reinitialization when performance drifts, and escalates to a person only when self-correction fails. The Controller does not hand out entanglement once and walk away; it keeps checking that the link stays healthy for as long as the application is using it, and reclaims the hardware the moment the job ends.”
The software control layer is essential to scaling quantum networking, according to Outshift by Cisco’s Reza Nejabati, head of quantum research and labs, and Sabitha Krishnamurthy, senior director of engineering.
“The transition ahead is not simply from smaller quantum networks to larger ones,” Nejabati and Krishnamurthy wrote in a blog post. “It is a transition from individually controlled quantum experiments to software-defined, programmable infrastructure—and Cisco’s Quantum Network Controller is a research prototype exploring what that operational layer could look like. The challenge ahead is not simply connecting quantum devices; it’s turning those connections into programmable network services. That’s why the path to practical quantum networking runs through the control layer.
The Controller utilizes the Universal Quantum Switch introduced earlier this year, which is designed to connect quantum systems from different vendors, such as IBM, IonQ, Google, and Rigetti, in all major qubit encoding technologies, at room temperature, and over standard telecom fiber. When two quantum computers need to share information, the Universal Quantum Switch accepts the signal in whatever modality it arrives, translates it into a common language for routing, and delivers it in the format the receiving system needs, without losing any quantum information along the way, according to Cisco.
In addition, a new version of Cisco’s Network-Aware Quantum Compiler prototype works with the controller to plan the quantum computation, “working out how much entanglement the network must deliver, between which nodes and at what fidelity,” Pandey wrote.
Sam Olds and Eneet Kaur, software engineering technical leaders at Outshift by Cisco, added details about the compiler’s role: “Cisco’s Network-Aware Quantum Compiler treats the network as part of the compilation, not an afterthought—partitioning and scheduling decisions are now made against a real model of switches, fiber, and finite entanglement instead of an abstract connectivity model,” Olds and Kaur wrote in a blog post.
“This release adds a full distributed error-correction package: when two surface-code patches sit on different quantum processing units (QPUs), the network operations needed to measure the seam between them become part of the logical error model, so the Compiler can plan for them instead of discovering them after the fact,” Olds and Kaur wrote.
