Cisco is layering control on top of its quantum networking gambit, rolling out a pair of abstraction updates designed to help mollify quantum’s vast tangle of entanglement.

The main update is the launch of Cisco’s Quantum Network Controller, which is designed to manage the supply side of the network. It acts to abstract the underlying physical hardware – with a special mention of Cisco’s recently introduced quantum switch – tracking available network topology, optical channels, and quantum resources so the network can allocate entanglement traffic across a multipoint deployment architecture.

Cisco describes the controller’s specific job as exposing an interface for each device category with a hardware abstraction layer underneath, which provides a “universal interconnect for any vendor’s hardware.” Those device categories include sources, switches, detectors, and timing systems.

That abstraction considers an application’s request for entanglement, endpoint names, rate, fidelity, and timing without the need for knowing how those factors are produced. That’s important as information in a quantum state cannot be read without destroying it.

“The controller cannot inspect traffic the way a classical monitoring tool would,” Cisco explains. “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.”

Vijoy Pandey, SVP and GM for Outshift by Cisco, described the controller as providing the “brains” for quantum networking hardware, something that is required to deal with all the components that will make up “quantum scale.” That scale is in both terms of the amount of information being transmitted by an application and the difficulty in maintaining insight into that data so it can be synchronized across various quantum entanglement avenues.

“The switch allows for physical scale, [but] where is the brain that allows for logical scale?” Pandey asked rhetorically. “Let's say you are doing something with or without the switch, but you have 10 nodes … and across those 10 nodes … I am now trying to synchronize timing. I am now trying to synchronize coherence because photons decohere and they disappear, and sometimes they don't even appear as entangled. … Or some pair of nodes are using more entangled photons, and some are sitting quietly, but suddenly these two start exchanging quantum information, so suddenly they need entanglement. You are now looking at a scaled environment where applications have an intent.”

That is where the controller takes the intent of those applications and for the endpoints to guarantee “that intent across a many-to-many infrastructure but also maintain that guarantee across the many-to-many infrastructure and maintain that guarantee across many application endpoints.”

“It's a multitenant, multi-application, intent-based controller for the quantum world operating in the quantum world, and it's built in such a way that it's not just controlling the devices we own and provide, but everything else that you need for the network to be relevant and maintainable and operable, so partners that provide other pieces of the ecosystem, whether they're detectors, other kinds of sources, best state measurements, and so on,” Pandey added. “So it's a controller for not just Cisco entities, but for the network itself.”

This ability was initially proven as part of trial earlier this year with Qunnect where Cisco integrated its unified quantum networking software stack to provided automated control and synchronization across multiple network nodes running on Qunnect’s New York City network.

Compile that control

Cisco also unveiled its Network-Aware Quantum Compiler, which acts as a “first-class citizen” on the controller to further this quantum networking simplification push.

The compiler works as a “demand-side application for quantum networks” that takes quantum algorithms and determining how to divide and schedule those algorithms across multiple quantum processors based on real-time network conditions. It does this as a “general-purpose” interface that “treats every application the same way, including a third-party compiler.”

Pandey noted that this agnostic feature is important as “every compute vendor out there has compilers that takes care of only their island.”

“But if you are going to enable just like cloud, if we're going to enable distributed quantum computing, we need compilers that take an application or circuit, provision compute across this distributed environment, partition that circuit across that provisioned environment, and schedule that partitioned entity across that entire environment,” Pandey explained. “Then once each part is done, collect the results and then report on the results across that, this is distributed computing 101, but that did not exist.”

Pandey added that the compiler is a “first-class citizen” on the controller, acting in an integrated fashion to orchestrate this flow of traffic.

“Instead of the compiler doing those acrobatics and running out of breath because it's a hard thing to do, the compiler just says, ‘I got this application intent. Controller, make it happen,’” Pandey explained. “And … the network part of it, the controller takes care of it, maintains it. The compiler only worries about the workload side of the equation.”

Both platforms remain “research prototypes,” meaning Cisco is not shipping these at scale, but rather is working with partners on a case-by-case basis.