PsiQuantum has a plan to make a massive quantum computer out of light

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James O'Donnell writes, PsiQuantum has a plan to make a massive quantum computer out of light.
The machine that could change the world will be housed in a room that looks like a data center crossed with an ice cream factory. Inside will be some 100 stainless steel cabinets, each about six feet tall, and connected to a supply of liquid helium that keeps them only a few degrees above absolute zero. Inside those cabinets will be hundreds of chips, and on those, thousands of particles of light flying through a maze of optical switches and beam splitters. Each photon must be accounted for, because precisely measuring where it ends up will help answer questions that current computers might take millions of years to solve. This computer, as described, does not exist. It is the brainchild of a company called PsiQuantum, founded in 2016 by four physicists from UK universities. In a crowded field of deep-pocketed competitors with similarly fantastical visions, the company aims to be first to fulfill its promise.
In the years since the physicist Richard Feynman first envisioned them in 1981, quantum computers have promised to speed up everything from medical research to AI, by harnessing the qualities of quantum particles. Unlike normal computer bits, which can be either a 1 or a 0, quantum bits can exist in multiple states at once, and combining enough of those quantum bits together, could produce a computer capable of tasks well beyond the reach of today's conventional machines. But even today's best quantum prototypes are too small and error prone to do anything useful.
That makes PsiQuantum's promises for what its computers will ultimately do all the more bold. Consider the company's hopes for predicting the effects of cytochrome P450 enzymes, which often break down drugs in the body. If pharma companies knew more precisely how they would work on a particular molecule, they could design more effective medications faster. Estimating this for a specific drug can take over 10 years of today's methods, says Philip Ernst, Vice President of Quantum Applications for PsiQuantum. But we aim to get it down to 4 minutes.
In a field full of such claims, PsiQuantum has attracted unusual investment and scrutiny for two reasons. It is one of the few companies aiming directly at building a large and useful machine. And it is already working with a major chip manufacturer to build its systems using existing semiconductor fabs. Its vision has attracted momentum. In 2025, PsiQuantum raised $1 billion in funding and broke ground in Chicago on a site it's building in partnership with local governments. It also has a second site in the works in Australia, which it promises will be operational, meaning hardware ready in 2027 And it's one of just two companies, along with Microsoft, to reach the third stage of an intensive government evaluation program to see which quantum companies might succeed.
Evaluating whether PsiQuantum will do what it says is harder than, say, judging a drug maker by its clinical trial results. Advances in quantum computing are incremental, opaque and tough to verify from the outside. But the company is now approaching its prove-it moment, when years of closed door work and hundreds of millions in investment will either culminate in a useful quantum computer or fall short. We could start to know which as soon as 2027
Terry Rudolph, one of PsiQuantum's four founders, is soft-spoken and shaggy-haired. He was born in Malawi and learned only after earning his first physics degree, that he is a grandson of the famed physicist Erwin Schrödinger. He later self-published a 150-page book to explain quantum computing to teenagers. My PR contact gave me a signed copy with a wink that said, We never expect anyone to actually read this, but I can report that it is a funny and helpful book.
Around 2014, Rudolph and his co-founders became increasingly convinced that the quantum breakthroughs they were finding to be possible in theory, might also be possible in a real machine. They eventually left their academic positions and divided the tasks before them. Rudolph worked on theory, Mark Thompson on engineering, Pete Shadbolt on scaling the technology up, and Jeremy O'Brien on articulating the vision and finding investors. O'Brien served as CEO until February 2026 He's been replaced by Victor Pung, a veteran of the semiconductor industry.