Scaling up quantum computing requires a fast interconnect, and diamonds may be the answer.

While a lot of attention is put on error correction, reducing noise and increasing qubit numbers, building out commercially useful quantum computers not only requires reliability but also the removal of bottlenecks is essential to fully realizing multi-core quantum computing.

“Before we’re going to get any real economic value out of quantum computers, we need some sort of interconnect solution,” Mihir Bhaskar, CEO and co-founder of Lightsynq, told EE Times in an interview.

At a high level, the problem is conceptually the same as with classical computing, Bhaskar said, and how quantum computing will be built out is not dissimilar to how data centers are being built today. He said Lightsynq is essentially trying to build an interconnect solution much like InfiniBand.

Rather than trying to link GPUs together in an optical network to harness the full power of the individual processors, Lightsynq is building a different process to connect quantum processing units. “Where the differences start to kick in is you do need a new type of InfiniBand technology that’s able to support that high bandwidth communication of quantum signals,” Bhaskar said.

Just as classical computing deals with bottlenecks, which can be a result of memory, processing or networking capabilities, the network is a bottleneck for multicore quantum computing processors, even though they do not yet exist, Bhaskar said. “The reason that quantum computing companies aren’t even able to build multi core systems with the technology they already have is because that network is just orders of magnitude slower.”

Quantum computers operate on slower timescales than classical computers, anywhere between kilohertz and megahertz, while networking technologies are down in the hertz range, which bottlenecks the processors, Bhaskar added.

Lightsynq is building a higher bandwidth networking solution to eliminate the bottleneck so information and can be exchanged between cores to perform distributed processing.

What makes solving the problem somewhat straightforward is that quantum computers use optical photons for communicating. “That’s really the only way of sending quantum information from one physical location to another.”

However, massive amounts of light are not required, Bhaskar added. “It’s actually the weakest amount signal you could possibly imagine. It’s single optical photons traveling through these fibers at one at a time.”

He said if there is any optical loss, it is primarily in the interfaces to the quantum computers, which causes the bottleneck. That is where Lightsynq’s hardware comes into play to speed up the rate of communication between different cores.

The company is borrowing from traditional data center concepts, except that new functionality is needed for a quantum interconnect that cannot be met by silicon, Bhaskar said. This is why Lightsynq turned to diamonds.

Although they are usually clear, diamonds can be found in a range of colours in nature, and for technological applications, different diamond colours are linked to different characteristics. Synthetic diamonds provide all the tools needed to create complex quantum connections due to the stability of their properties and the ability to interact with light, Bhaskar said.

Lightsynq’s synthetic diamond provider, Element Six (E6), recently announced investment into the quantum interconnect startup, which is the extension of a long-standing research collaboration with Lightsynq founders’ team, Bhaskar said. E6’s engineered materials will allow Lightsynq to build its interconnect by leveraging technical capabilities in synthetic diamond manufacturing. “We’ve learned and developed a lot of the techniques and intellectual property around how to fabricate photonic integrated circuits in diamond.”

E6 has demonstrated that it can grow a quantum-grade diamond through chemical vapor deposition techniques and could contain color centers that enable in-memory computing. These color centers have desirable properties of being able to be written to, manipulated and read out with existing semiconductor solutions, enabling interconnects that do not require disruptive redesigns of existing quantum hardware.

E6’s synthetic diamonds are compatible with quantum devices across various platforms, from atoms, ions and photons to superconducting circuits with optical interfaces.

Bhaskar said the recent investment from E6 will enable Lightsynq to take what it has already done at a small scale and show that it can manufacture diamonds in a way that can be translated to larger scales. “We don’t know of another technology that has the performance in terms of a quantum interconnect as diamond.”

Lightsynq is not the only company developing technology to help quantum computing scale up. Canada’s Photonic Inc. is now able to tap into Telus’ PureFibre infrastructure to accelerate the development of next-generation quantum communications. The dedicated access to an advanced fiber-optic network will enable the Vancouver-based startup to test its quantum technologies and real-world applications.

FROM EETimes