Cisco took the wraps off a working research prototype for a switch that it claims is the biggest missing piece for building quantum networks and could accelerate the arrival of practical quantum computing using telecom networks.
The Cisco Universal Quantum Switch can interconnect quantum computers from any vendor to create distributed quantum computing networks. It routes and preserves quantum information for all encoding and entanglement modalities, at room temperature and using existing fiber infrastructure.
The company says the technology is the first switch of its kind and is aimed at expanding quantum computing through distributed networks.
It argues that future quantum use cases will need far more qubits (quantum bits) than quantum computers have today. This limitation can be addressed by scaling up and building bigger computers as well as by scaling out through quantum networks, and both are necessary, according to Cisco.
The idea is that by connecting quantum computing nodes through a quantum network, they “share a common state, and they appear and behave as one large quantum computer,” said Vijoy Pandey, senior vice president and general manager at Outshift, Cisco’s emerging technologies and incubation group.
A key part of its approach to quantum is that the technology is designed to be inserted into today’s telecom networks, so that “the quantum network and classical network sit side by side on the same physical infrastructure,” he explained.
Not lost in translation
Quantum networks will need a different kind of switch because optical switches available today “always mess with the quantum encoding and how the quantum [information is] mapped to the photons in the network,” said Reza Nejabati, head of Cisco’s Quantum Labs and quantum research.
One of the “very unique” features of the prototype switch is that it translates various encoding modalities into a common language for routing while preserving the quantum information.
Underpinned by Cisco’s patented “conversion engine,” the switch can support all quantum encoding modalities: polarization, time-bin, frequency-bin and path. This enables quantum computing systems from different vendors to be connected and interoperate via a quantum network.
The switch operates at room temperature, unlike quantum hardware that needs cryogenic cooling, so extra cooling infrastructure is not needed. Further, it operates at “standard telecom frequencies” on existing fiber networks.
Pandey believes that “distributed quantum computing will be the norm,” and that it will come either through a cloud service offering or as an on-premises deployment with quantum compute nodes attached to it. “What stays common and uniform is a quantum network,” he said.
This quantum network vision places Cisco’s telecom customers in the action of future quantum computing.
“Telecom providers have a really big role to play here … I cannot reiterate that enough, because starting from the hardware, which is room temperature, existing telecom frequencies on existing fiber – we are handing that as a present to our customers. What we’re saying is, you don’t have to create a brand-new quantum network and rebuild fiber infrastructure to make that happen,” said Pandey.
That is, packet-based networks that transfer bits can run alongside teleportation- and entanglement-based quantum networks on the same fiber infrastructure.
Real-world tests
The universal switch is being put through its paces in experiments in the lab and real-world environments. Recently, Cisco researchers tested the switch for “entanglement swapping” over a 17.6-kilometer fiber network between Manhattan and Brooklyn, starting from the carrier hotel at 60 Hudson Street in New York. The results were “substantially better” than lab demonstrations, the company said.
Experiments have also shown that the switch preserved quantum information with “less than 4% degradation in quantum state fidelity and entanglement, maintaining the coherence that quantum networks require to function.” It has also achieved sub-nanosecond “electro-optic” switching and consumed less than 1 milliwatt of power.
As a working research prototype, the switch is not commercially available.
The device is part of what the company calls its quantum network stack, which is being developed by Cisco’s Quantum Labs and includes hardware, management software and applications. The technology stack comprises a quantum network entanglement chip, announced in May last year; the “network-aware” Quantum Compiler; and two quantum applications, called Sync and Alert.
For its quantum network work, Cisco is working with partners Atom Computing, IBM and Qunnect.