Microsoft Corp.’s M12 venture capital arm and a number of other prominent investors have bet $215 million on PsiQuantum Corp., a startup aiming to build a million-qubit photonic quantum computer within a few years.

The investment was first reported by Bloomberg today. It makes PsiQuantum one of the most well-funded startups in the quantum computing ecosystem.

Palo Alto, California-based PsiQuantum is a developing quantum computer that uses photons as qubits. It’s an approach that differs fundamentally from the implementations of the current leading players in the field. Honeywell International Inc.’s quantum computer, which the company has said will soon be the fastest in the world, uses trapped ions as qubits, while Google LLC’s Sycamore relies on superconducting circuits. 

The brains of PsiQuantum’s system is a custom silicon chip intersected by tiny mirrors. Photons travel along pathways on the chip and the mirrors “bounce” them into an entangled state, the startup told Bloomberg, thus facilitating computation. A sensor that measures the entangled photons allows PsiQuantum to perform calculations and read their output.

Quantum entanglement is a physical phenomenon wherein two particles that interact with each once sync up and stay linked even at long distances. If an entangled qubit changes its spin, for instance, the spin of the qubit to which it’s linked will change as well. Quantum computers use this effect as a processing shortcut to speed up calculations that are difficult for classical computers to perform.

PsiQuantum says that its approach has two major advantages over the competition. One is that its mirror-laden chip can be made using existing semiconductor fabrication equipment, which eases manufacturing. The other advantage PsiQuantum touts is scalability: Chief Executive Officer Jeremy O’Brien said that he believes his team can build a quantum computer featuring a million qubits within a “handful of years.”

PsiQuantum has already started manufacturing quantum chips with the help of fab operator GlobalFoundries Inc. The startup is now said to be working on developing the other components necessary for a quantum computer, including networking equipment and quantum software. PsiQuantum expects that the complete 1 million-qubit system will be the size of a conference room and contain 100 to 300 error-corrected qubits reliable enough for processing tasks.

Such a device would leapfrog rivals such as Google’s Sycamore in performance, assuming it lives up to the promise. But the time PsiQuantum will take to build a functioning system will give rivals room to enhance their technology.

It’s worth noting that Microsoft, one of the startup’s investors, is developing its own quantum computer using a different approach. Buying a stake in PsiQuantum allows the company to hedge its bets and double its chances of finding a path to commercial quantum computing. 

“PsiQuantum and Microsoft have different sets of engineering challenges to address with their distinct approaches, but the companies share the vision for a scalable, fault tolerant quantum computer,” Samir Kumar, the head of the tech giant’s M12 venture fund, wrote in a blog post.

Besides Microsoft, PsiQuantum is backed by Playground Global, Atomico, Founders Fund, Redpoint Ventures, and BlackRock Advisors.

Photo: PsiQuantum