Quantum networks have been in the news a lot lately. The latest news comes from Cisco, which has revealed a whole new approach to routing that the company plans to implement to support quantum networks.
Cisco’s vision is driven by the belief that powerful quantum computers now emerging will be even more powerful if they can be interconnected. The same networks also could connect quantum sensors and support applications involving security and synchronization, according to Cisco’s vision.
Initially, quantum networks are likely to exist within data centers. But as Cisco executives explained on a pre-briefing webinar with reporters on Monday, the technology that the company is developing could interconnect locations separated by distances as great as 100 kilometers. It’s designed to work over telecom wavelengths on commercial fiber networks.
The Cisco quantum switch
Currently, quantum network endpoints are connected on a point-to-point basis akin to the switchboard approach used in the early days of telecom. Cisco’s news today focuses on a prototype quantum switch that aims to offer a more powerful option.
Ramana Kompella, Cisco’s head of research, offered a clear explanation of why traditional routing methods such as TCP/IP are not appropriate for quantum networks.
Essentially, the reason is that quantum networks are based on quantum physics. A key concept of quantum physics is entanglement. Quantum network endpoints are connected using entangled photon pairs — one at each end of the connection. Once entanglement has been established, information is transferred instantaneously from one endpoint to the other.
As Kompella explained, “In quantum, you have entanglement distribution, which isn’t used in classical [networking]. You need an entanglement source to convey the entangled photons that need to be distributed to two parties that want to communicate.”
In contrast, he said, “In the classical world, you take a bunch of bits, put them in a packet, shove it down the network, and the network can figure out a way to the destination.”
With quantum networks, he said, “You have to establish an end-to-end path between two nodes that want to communicate. Entangled photons need to be delivered to these endpoints and then they use teleportation to transfer information.”
The role of the quantum switch, he noted, is a bit like the role of a circuit switch in telecom.
“You have to establish an end-to-end path,” he said.
He also noted that, “It’s not TCP packets that go through the switch. It’s photons going through the switch.”
The prototype
While some quantum computers must be kept at extremely cold temperatures to work properly, Cisco’s switch operates at room temperature.
The switch is also designed to interconnect quantum computers that use different coding modalities. Quantum computers from different manufacturers use different methods of carrying information. Encoding methods that the Cisco switch is designed to support include polarization, time-bin, frequency-bin and path. The goal is to enable computers that weren’t designed to work together to do so.
Executives on the pre-briefing webinar declined to say when the switch would be commercially available.
“There are so many fundamental inventions in the switch — the conversion, the preservation of quantum state — that we have to first prove it out,” said Vijoy Pandey, senior vice president and general manager of Cisco’s Emerging Technologies and Incubation Group.
For the next one to two years, the company wants to work with partners such as IBM and Atom Computing to “showcase distributed quantum computing end to end,” Pandey added.
During that period, Cisco also wants to work with partners to showcase use cases such as security and synchronization, he said.
