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

Welcome to MIT Technology Review Narrated. My name is Matt Honan. I'm our editor-in-chief. Every week, we'll bring you a fascinating, new, in-depth story from the leading edge of science and technology, covering topics like AI, biotech, climate, energy, robotics, and more. Here's this week's story. I hope you enjoy it. Narrated by NOAH. Listen to more of the best articles from the world's biggest publishers on the NOAH app. Or at newsoveraudio.com. James O'Donnell writes, "Sci Quantum 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 6 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 4 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 with today's methods," says Philipp 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 drugmaker 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 Peng, a veteran of the semiconductor industry. To understand why the quantum computer the company is building would be a big deal, consider how imprecise much of modern science remains. We cannot reliably predict, for example, which lithium-ion battery will catch fire, or how quickly a critical aircraft component will corrode. This isn't just because these systems are complex, though they are. It's that, at their core, they are governed by quantum mechanics, Subatomic particles don't have well-defined properties—this location and that velocity—but instead occupy quantum states spread across many possibilities. And that, in turn, influences a range of atomic and molecular behavior. Schrödinger—Rudolf's grandfather, remember?—showed how to describe this haziness mathematically a century ago this year. But precisely carrying out the calculations on real-world systems quickly becomes unfeasible even for the best computers. Scientists cope with this gap using approximations, imperfect simulations, or experiments on animals. Feynman, David Deutsch, and other physicists in the 1980s wondered if we could do better. Maybe such complexity could instead be modeled using a new kind of machine. Rather than using transistors that are only ever on or off, This one would use particles held in quantum states, manipulate them to perform calculations, and then measure them at the end for an answer. Using quantum systems to simulate quantum systems would for the first time allow a simulation of physics and chemistry that directly reflected reality. It would be an invaluable tool for designing new drugs, materials, or really anything affected by quantum mechanics. Revolutionary, in other words. Humankind's leaps in understanding how nature works have often resulted in the invention of powerful new tools, Rudolph told me. I don't think it's coincidence that the Industrial Revolution coincided with our ability to calculate and simulate the laws of Newtonian mechanics, the laws of thermodynamics, the laws of classical electromagnetism, he says. Whenever we have more power to calculate and simulate and understand things We build incredible machines that come from that. He sees something similar coming with quantum computers. One mystery has always been which quantum thing—ions, atoms, or something entirely new engineered with quantum properties—could be made stable and controllable enough to use as a qubit, the basic unit in the quantum computing world. Quantum systems are delicate, and observing any particular particle causes it to collapse into one state rather than a superposition of multiple states. If this happens during the computation rather than at the end, it produces an error that must be corrected for. Too many of these means the computer fails to produce a useful answer. Just as engineers in the early days of aviation weren't sure whether airplane wings would be fixed or flap like a bird's, We're not yet sure which of these quantum things will work best. Google and IBM are betting on superconducting qubits—superconducting circuits made of aluminum or other metals. Intel is using electrons. PsiQuantum is using photons, the particles that make up light. Photons have lots of nice things going for them, Rudolph says. They can maintain quantum states for a long time. Indeed, the photons in the universe's cosmic microwave background may have done so for billions of years. But photons also move fast and scatter easily. More importantly, two photons are more likely to pass through one other than interact. That makes them a challenging candidate for quantum computation, in which qubits need ways to influence one another. For a while, this last flaw seemed to doom the idea of quantum computing with light. But in 2001, researchers from the Los Alamos National Laboratory and the University of Queensland found a loophole. They discovered they could essentially "fake" interactions between photons by sending the light particles through a network of beam splitters and detectors. Their paper changed everything. PsiQuantum was created to make the theory a reality. Size was the first problem. Previous plans would have required a computer as large as California. Mercedes Jimeno Segovia, who was a PhD student of Rudolph's in the early 2010s, after almost becoming a professional violinist instead, thought of a way for the machine to be smaller. The basic process since then has been this: first, create photons with lasers and then entangle them, exploiting a quantum phenomenon in which the particles no longer have individual states but instead share one. Next, route them through a maze of gates that perform computations, and finally, read out details of their quantum state at the end, all while tracking and correcting for the errors that occur. Succeeding at each of these steps millions of times is not so much an engineering hurdle as a brick wall. And building the supply chain, like manufacturing new materials with the qualities to route individual photons around, is arduous. To get a sense of it all, in 2025, I joined Shadbolt at the SLAC National Accelerator Laboratory in Menlo Park, California. The center has helped produce several Nobel Prizes and played a role in the 1968 discovery of quarks, fundamental building blocks of matter that make up protons and neutrons. But PsiQuantum set up shop there essentially to siphon liquid helium from SLAC's giant cryo plant. This is what the company uses to cool its computing cabinets down to deep-space temperatures. Right now, the cabinets operate at 2K, or -456°F, but the goal is to be able to run them slightly warmer, at a balmy -452°F. Most quantum approaches require the whole machine to be coded to superconducting temperatures, so that much of the expense in running it will actually be spent on refrigeration. But photonic computers require only one piece to be this cold: the detectors that measure single photons at the end of the computation. And the required temperature can be a bit higher. PsiQuantum said in May 2026 that it will spend some of the $100 million award in CHIPS Act funding it's slated to get on these detectors. The siphoning setup was a temporary solution. PsiQuantum now has its own cooling system at its testing facility in Milpitas, California, and is setting up a larger one at its production site in Australia in 2027. These helium systems represent some of the biggest capital expenditures for any quantum company and will consume a significant chunk of PsiQuantum's $1 billion funding round. In the afternoon, we drove to a lab in San Jose. Where I donned a cleanroom suit—a head-to-toe covering that keeps dust at bay—to watch the manufacture of a bluish crystal called barium titanate. It's prized by PsiQuantum because it quickly and reliably routes light particles with very little electrical input, keeping the precious photons undisturbed as they move through the circuit. But for all barium titanate's theoretical value to the company, Its structure makes it a pain to manufacture, and the material wasn't available at scale when CyQuantum got its start. The company, in what Rudolph told me was an agonizing decision, opted to make it in-house, requiring a massive investment. I saw a technician operating at what looked like a giant pressure cooker, adding the base elements to several hoppers. Then I watched through a porthole as the elements got heated, vaporized, and finally crystallized into a thin layer on a wafer disk. At that time, each disk took about 12 hours to make. The company now says several are produced each day. The disks then get shipped to the chipmaker GlobalFoundries in Malta, New York, where CyQuantum's chips are made. CyQuantum's bet is that this entire supply chain, Byzantine as it might sound, will make the company more efficient than its competitors, That's because, if you squint, it looks like a souped-up and high-precision version of the existing supply chain for silicon photonic chips, another type of technology that transmits information with light, one that's already used in data centers. If PsiQuantum produces its chips at scale, it can take advantage of tools and infrastructure that already exist. But it's not a given that one working chip can easily be wired up to thousands more. That's why the company is testing in phases. Its Milpitas site has connected 3 cabinets together, with 250 chips in each. But the next step is to scale the systems up and see whether the company's techniques for correcting errors can keep up. Once the cooling system arrives at the Australian site in late 2027, the company says, it aims to connect about 100 cabinets together. Then PsiQuantum will work up to running the world-changing algorithms it has promised. The timeline for this, it's worth noting, is up for debate. News articles have said that 2027 is the year that PsiQuantum aims to have its first full-scale quantum computer come online at its Australian site. But the company insists the deadline has been misread, and that it only intends for its facility to be operational by the end of 2027. That means cooling systems in place and ready for hardware to be installed, but no promises about what size computer will be ready. In an industry where timelines are perpetually in flux, yet central to how companies are judged, that distinction isn't trivial. The outsider with perhaps the best guess of whether PsiQuantum will succeed is the Pentagon. The U.S. Defense Advanced Research Projects Agency, the Pentagon's research and development arm, has been running an initiative to determine which of the boastful quantum companies might actually deliver. In the last year and a half, the heads of the program have been sounding more confident. Joe Altipeter, who ran the program until 2025 and proudly described himself as a "quantum skeptic," told me in March 2025, "I am more optimistic now than I have been at any point in the past 10 years." And in a statement earlier in 2026, his successor, Michael Stoudemire, said it now seems likely that someone will build a utility-scale quantum computer by 2033, referring to a machine that generates more value from its calculations than it costs to build and operate. The program has been scrutinizing PsiQuantum's systems for over a year and putting them through the third stage of a benchmarking initiative meant to determine whether the technology will actually work. But to the rest of the industry, PsiQuantum is sort of a black box. It is very hard for an outsider to evaluate, says Scott Aaronson, a theoretical computer scientist at the University of Texas at Austin who runs a popular blog that often covers the industry. Other companies like Google and Quantinuum have regularly published results over the years demonstrating chips and systems with incremental improvement. Publicly laying the engineering groundwork needed to eventually build large machines. PsiQuantum has instead focused squarely on a commercial goal: a computer with 1 million qubits, which is the scale that researchers expect to unlock research currently not possible on normal computers. PsiQuantum often differentiates itself with this industrial-scale goal, but IBM, which debuted a development roadmap in 2020, has been progressively building bigger and bigger systems. It initially targeted 2028 for a large-scale, error-corrected system, a deadline that now appears to have been pushed out to 2030. On top of actually building the machine, a major focus for PsiQuantum is getting the rest of the world to develop a plan for how to use it. PsiQuantum has announced partnerships with customers including the defense giant Lockheed Martin. Which intends to use it for materials design, the automaker Mercedes, which wants it for battery design, and the aerospace manufacturer Airbus. That these companies don't have a computer to experiment with is not a problem, according to Ernst at PsiQuantum. There's a PlayStation 6 probably coming up from Sony next year or the year after, and people are programming those games right now, he says. This is in principle very similar. It's a glib analogy, but not an entirely empty one. The quantum algorithms for solving a research problem can be tracked even if there is not yet hardware to run them on. The idea is that experts in quantum information, from both PsiQuantum and its customers, will be able to translate design problems—say, the requirements for a battery in a Mercedes electric vehicle—into algorithms the computer could solve. The company offers a software package called Construct, which companies can use to design their own algorithms that might one day run on their computer. The future of quantum computing hinges on these algorithms. Quantum computers get painted as a speedup for everything, but in reality, they're suited to a subset of problems, and answering a question with this sort of machine requires the question to be formulated with very specific types of algorithms. People spend entire careers working on such algorithms, even if the computers to run them don't exist yet. At their core, they use the rules of quantum mechanics to manipulate probabilities in ways that ordinary computers can't. The most famous example, and a reason the government is so interested in quantum computers, is Shor's algorithm. It was developed in 1994 by the theoretical computer scientist Peter Shor and could effectively break many forms of encryption used online for everything from credit card numbers to military intelligence. The thing keeping the world together for now is that nobody has a computer to run the algorithm on, and security experts are already launching new encryption methods that could withstand attacks from a quantum computer. PsiQuantum is researching how long its systems might take to run Shor's algorithm. The company also published a paper in December 2025 in collaboration with Airbus, essentially seeing if a new algorithm developed by the authors could beat a classical computer in modeling fluid dynamics, like the turbulence around an airplane wing. Andrew Childs, an expert in quantum simulation, told me PsiQuantum achieved only a moderate speed increase over what today's computers can do, "It's probably unlikely that speedups like this will have a significant practical impact until we have very large-scale quantum computers," he said in an email. When I asked Ernst, he agreed the improvement was modest. Some of the algorithms PsiQuantum is working on are not expected to be perfected or even used in the first applications of its computer. Instead, its initial tasks might be more along the lines that Feynman envisioned way back in 1981. Simulating the smallest particles of our world. The company's most significant research in this realm is in modeling quantum chemistry. Take those pesky P450 enzymes. More precisely understanding how they operate, PsiQuantum says, would allow for faster drug development and testing. In 2025, PsiQuantum published methods for doing these sorts of chemistry calculations on a quantum computer. Along with another paper demonstrating an algorithm that can simulate the collision of two molecules and estimate the likelihood of different outcomes femtosecond by femtosecond. There are 1 quadrillion femtoseconds in a second. It's a remarkable amount of detail not currently possible with today's technology, and it would allow drug and materials researchers to simulate new chemical interactions. Dominic Berry, who developed some of the core techniques used in the collision paper but isn't involved in PsiQuantum, says the company made impressive improvements, but to do the simulations scientists are most curious about would require the algorithm to be made even faster in PsiQuantum's early computer to have fewer errors than currently expected. Until PsiQuantum's computers are up and running, the breakthroughs that these research papers tease remain in the realm of theory. It's a space where Rudolph operates quite comfortably. He told me that Alan Turing created the theory of classical computing with pen and paper, imagining how the ones and zeros would be represented in the machine and how, with the right approach to logic, you could compute almost anything. But there is no way that by hand with a pen and paper Turing was ever going to produce, you know, Minecraft and Facebook, he says. That took more than 70 years of tinkering, during which we fortunately created more useful things than Minecraft and Facebook. For all the time Rudolph spends dreaming up things quantum computers might do, in other words, people working on those problems are still stuck with pen and paper for now. Until you have the actual machine in hand, you don't have the opportunity to really explore its potential. You were listening to MIT Technology Review, where James O'Donnell writes, PsiQuantum has a plan to make a massive quantum computer out of light. This article was published on July 14, 2026, and was read by Sam Scholl for NOAH.