DARPA seeks universal translator between different kinds of quantum computer

WASHINGTON — What if no one wins the quantum race?

Looking at all the competing approaches to building a quantum computer, it’s possible that one day the dust will settle and one competitor will have produced “the One Ring to Rule them all,” said DARPA program manager Justin Cohen: the perfect all-purpose quantum bit or “qubit” for all the technology’s potential applications. “Maybe,” he said.

But he’s betting taxpayer dollars against it. Instead, Cohen told Breaking Defense, “I’d say that it’s pretty clear that, on any kind of timeline that we have clear insight on, there will be no perfect qubit species or modality.”

So while rival companies each strive to perfect their own proprietary tech, Cohen has launched a DARPA program, called Heterogenous Architectures for Quantum (HARQ), to fund both the hardware and software required to combine different quantum technologies into a single device. He and his team are currently reviewing proposals, with multiple awards of up to $2 million apiece expected to come out by Feb. 1.

The program’s ultimate goal: The namesake “heterogenous architecture,” an overarching structure can blend the best of multiple approaches into a harmonious whole. Instead of the One Ring from Tolkien’s embattled Middle Earth, think of it as the Universal Translator from Stark Trek’s utopian Federation.

The real-world stakes are high in this quantum quest. Companies and countries round the world are racing to build the first high-powered quantum computer, a device that could potentially crack the encryption underpinning the internet, solve previously intractable optimization problems in industrial or military planning, and model hitherto unimaginable molecules to make miracle cures — or deadly new designer pathogens.

But different competitors are taking a bewildering variety of technical approaches, building qubits out of such esoterica as (deep breath now) superconducting aluminum, electrically charged particles (trapped ions), uncharged particles (neutral atoms), electrons (sometimes organized in “quantum dots”), and even the intangible particles of light itself (photons).

Each kind of qubit has different strengths and weaknesses: Some kinds of qubits are more stable, some require less elaborate cooling systems, some can transmit information better across a network or between different components of the same device, and so on. (This 2024 series of papers from Mitchell Institute Senior Fellow Heather Penney has a solid summary for lay readers). Even where two companies are using the same kind of qubit, they often have different implementations.

“Even if there’s some really amazing advances, which I think there will be in these individual qubit technologies over the next decade, it will still be the case that there are some species that are more naturally suited to different functions, like memory, like processing, like data movement between modules,” Cohen said.

That’s very similar to the mix of different technologies that have to work together in current computers, he added. The transistor was invented in 1947, but even today “we still don’t have one transistor to rule them all,” he said. “We still pick different technologies, different hardware, to run different part of a classical computer. [So] let’s look at what that heterogeneity looks like for quantum computing.”

Specifically, HARQ seeks to fill the gaps in how the private sector’s been investing.

“We’re not trying to compete with the development that they’re doing. What we’re hyper focused on is the interstitial pieces that could link up those systems,” Cohen emphasized. “We’re making these investments and directions that are not on the near-term road maps of any of these companies.”

In essence, while each major player focuses on perfecting its own approach, HARQ wants to build bridges between them. That includes three major types of technology: converters that can turn one type of qubit into another, memory modules that can store qubits long-term without decaying, and software to coordinate all the different components. Then, once HARQ’s award-winners have developed working prototypes — a process the program plans to take at least a couple of years — they can provide a new set of options to the quantum industry.

Cohen’s vision is that being able to interconnect different kinds of qubits inside the same device will open up new opportunities for cooperation and specialization in the industry.

“Now any one company doesn’t have to build every single part of the system, solve every problem,” he said. “They could sell the memory, or they could sell the processor,” or the connectors themselves.

And as a result, he said, “we can have more powerful systems, sooner.”