Not Quantum, Not Classical: This Light-Based Computer Is Something Else Entirely

In a world of ever-improving computing hardware—both classical and quantum—one team of engineers is veering off the familiar path. And the unusual device, based on a century-old physics concept, appears to be surprisingly capable of addressing some difficult computing challenges.

The new device, described in a recent Nature paper, is specifically an Ising machine. Based on the physics model of the same name, the processor uses pulses of light instead of binary bits to find the best mathematical solutions to real-life problems, such as protein folding, cryptography, or traffic routing. It’s made of relatively accessible components, operates at room temperature, and can juggle billions of operations per second.

“This breakthrough shows that it is possible to build a practical and scalable machine that can tackle extremely difficult problems,” the researchers said in a statement.

Realizing an old physics idea

The new machine’s specialty lies in optimization problems, or challenges in which the goal is to select the best option from a large number of potential solutions. One real-life example involves finding the most efficient route for delivering packages. The number of possible routes increases exponentially as the number of packages increases, so finding the best—optimized—route becomes increasingly difficult.

“With five stops, there are only 12 possible routes. With 10 stops, there are 180,000. With 20 stops, there are more than 60 million billion options,” explained Bhavin J. Shastri, study senior author and a physicist at Queen’s University in Canada, in the release.

When there are 50 stops, Shastri continued, that inflates the number of solutions so much that it’d take “longer than the age of the universe” to check them all. This is where an Ising model can come in handy.

This model represents such problems as a collection of interacting magnets whose spins point up or down. Over time, this collection of magnets naturally falls into an equilibrium that represents the lowest possible energy state. Mathematically, that translates into the most efficient solution to optimization problems, the researchers explained.

A “computer” running on light

Instead of magnets, the new device uses pulses of light that loop around the hardware and “gradually settle into a configuration that represents a good solution, much like a group reaching a consensus after many quick exchanges,” according to the researchers. “It’s a way to turn light into a problem solver,” Shastri added.

What’s more, the team built the system using components commonly found in commercial internet infrastructure, such as standard lasers, fiber-optic cables, and modulators. The resulting machine needed just five basic components to achieve 256 spins (65,536 couplings), allowing it to process billions of operations per second.

Impressively, the machine also remained stable for hours at room temperature. That’s a significant improvement over earlier Ising machines, as well as supercomputers and quantum processors that require extremely cold temperatures and specialized materials, the team said.

Optimized, just for specific tasks

All that said, the Ising machine won’t be replacing supercomputers and quantum computers anytime soon, if ever. As the team admits, the system is highly optimized for very specific applications and isn’t meant to be a general computing device.

Still, the practicality of scaling and operating the new system holds great potential for the problems it is good at solving, the team added. Accordingly, the researchers shared that their next steps are to develop pilot projects with industry partners to see how and whether the machine could address real-world optimization problems.