TORONTO — Xanadu says it’s figured out how to network quantum computers together, solving a key problem standing in the way of the technology becoming genuinely useful for businesses.

The Toronto-based startup’s new Aurora system consists of 35 photonic chips and 13 kilometres of fibre optics spread across four server racks. Xanadu successfully connected that hardware together to act as a single “baby data centre” without dropping critical information, said CEO Christian Weedbrook. 

The firm claims its method can scale up to the thousands of server racks required to form a quantum computer that can solve real-world problems. “No one’s done that before,” Weedbrook said. On Wednesday, Xanadu published its results in the journal Nature.

The promise of quantum computers is that they can run calculations significantly faster than traditional computers and tackle currently impossible challenges. Applications could include simulating chemical combinations to identify new materials, or cracking current encryption standards. But the technology currently has limited use.

One reason is that it can’t be scaled. When data moves between any two devices, quantum or otherwise, not all of the information makes it. That’s not much of a problem for, say, browsing the internet, but it’s a particular challenge for quantum computing, which must maintain entanglement—a condition in which particles stay connected even when they’re far apart—across the whole system.

“Our biggest challenge is how to keep the loss as low as possible,” said Weedbrook. Over the last year and a half, Xanadu has figured out how to minimize the information that drops when its servers are talking to each other. The firm’s use of photonics—different states of light—in its computing and networking hardware gives it an edge over competitors taking other approaches, Weedbrook said.

Founded in December 2016, Xanadu now has 220 staff and has raised US$241 million from investors including Georgian Partners, OMERS Ventures and Radical Ventures, according to PitchBook data. The federal government’s flagship Strategic Innovation Fund is also providing Xanadu $40 million in financing to develop its technology.

The startup currently has a cloud service on which companies can test out its technology. For example, Volkswagen has worked with Xanadu to develop algorithms that will simulate better battery materials once its quantum computer gets good enough. 

The startup is in the early stages of raising a new US$200 million round, Weedbrook said. Its goal is to start building a full-size quantum data centre in Toronto in 2029. 

Before it can do so, however, Xanadu must hit another major quantum milestone called fault tolerance. All computers make errors, but quantum computers are more prone to them than classical systems because of both the physics and the hardware they use. That means the complicated algorithms they’re running are likely to produce inaccurate results, with the risk increasing the longer they operate. 

Quantum computing firms are trying to build devices that make fewer mistakes and write code that can spot and fix them. Last month, Google announced a breakthrough in error correction. Xanadu has significantly improved the performance of its chips and other optical parts over the last year and a half, according to Weedbrook, but must make them better still to achieve fault tolerance. It also needs to bring down the cost of its hardware.

Still, figuring out how to connect thousands of server racks together into a single, giant quantum computer is a major advance, Weedbrook said. “The light at the end of the tunnel is getting far brighter.”