For The First Time, a Quantum Computer Has Operated in Space - ScienceAlert

For The First Time, a Quantum Computer Has Operated in Space Physics27 September 2026By Michelle Starr Like delicate flowers, quantum computers require carefully controlled conditions that are difficult to maintain in space. This zinnia was grown aboard the International Space Station. (NASA Johnson/Flickr) Space has a huge data problem.Many satellites in Earth orbit spend pretty much all their time collecting raw data – but sending it back to the ground is stymied by downlink bandwidth and how often a satellite can communicate with receiving stations. One possible solution to this problem would be to process the raw data right there on the satellite. Now, a team of physicists led by Philip Walther of the University of Vienna has demonstrated an audacious way to do so. For the first time, a quantum processor has operated in space. But it wasn't exactly easy getting there. Quantum computers are delicate little flowers. The quantum states they rely on are extraordinarily sensitive to their surroundings. Heat, vibration, electromagnetic interference, and other disturbances can disrupt those states, introducing errors or destroying the quantum behavior the computer needs to work. It's difficult to get right, even under the most pristine laboratory conditions. As you can probably imagine, space is a far less forgiving environment. The processor developed by Walther and his colleagues uses particles of light – photons – to carry quantum information. At its heart is a source that generates photons in pairs and feeds them into a programmable network of optical pathways etched into a tiny glass chip. For the processor to exploit their quantum behavior, those photons need to be indistinguishable from one another. Even tiny differences in properties such as their arrival time, polarization, or wavelength can allow them to be told apart, spoiling the interference on which the computation relies. And this needed to be accomplished on a satellite hurtling around Earth at 28,000 kilometers (17,400 miles) per hour under the punishing rays of the unfiltered Sun – after surviving the considerable mechanical stress of rocket launch. The only way to tackle these problems was going to be one piece at a time – with the rocket launch first on the menu.A diagram illustrating the team's quantum computing platform. (Steiner et al., arXiv, 2026)A rocket launch is a brutal way to transport a delicate optical device – strapped to a giant, heavy tube of reinforced material and accelerated to orbital velocity through Earth's atmosphere. The most robust suspension system we could build wouldn't stop it from vibrating maniacally. So, the best solution was to reinforce the instrument itself. The researchers mounted the most delicate components on tough titanium baseplates and reinforced the fragile optical fibers that feed into and out of the glass photonic chip with epoxy. Basically, anything liable to wiggle that absolutely must not wiggle was glued firmly into place. Then they shook the hecking jeepers out of it. Before launch, prototypes were subjected to vibration and shock tests designed to reproduce the punishment of a rocket ride. At one resonant frequency, the shock-response requirement reached around 1,500 times Earth's gravity. It worked. The optics emerged with no measurable degradation in their performance. On 23 June 2025, the computer was yeeted into low-Earth orbit at an altitude of about 510 kilometers aboard a Falcon 9 – and it turned out that rocket launch was going to be the least of its problems.The space-compatible quantum computing unit. (Steiner et al., arXiv, 2026)It all started going awry almost immediately. The instrument launched with six silicon single-photon avalanche diodes (SPADs), which detect the photons emerging from the photonic circuit – a pretty vital part of the experiment. But only three turned out to be usable. Then… the Sun happened. The remaining photon detectors were sensitive enough that the light of the Sun created a strong and wildly fluctuating background signal, drowning out the delicate measurements the researchers were trying to make. Fortunately, the satellite didn't spend its entire orbit in sunlight. Every 92 minutes or so, it passed into Earth's shadow, where the background noise dropped dramatically. That gave the team a window of about 30 minutes per orbit to take their most sensitive measurements. So far, so good. But while Earth's shadow solved the sunlight problem, it couldn't do much about the radiation environment of low-Earth orbit – the concentration of energetic protons and electrons trapped within the confines of the Van Allen belts. The researchers had anticipated this, too, encasing the payload in a centimeter-thick shield of aerospace-grade aluminum. It worked pretty well against the electrons – but protons are considerably more difficult to block without adding hefty amounts of weight. Sure enough, the surviving photon detectors began to deteriorate. After 52 days in orbit, their dark count rate – false detections generated even when no photon arrives – noticeably increased. The researchers were able to compensate by adjusting the voltage supplied to the detectors, clawing back some of the lost signal. But then there was the laser.

The team had used a commercial laser modified to withstand the mechanical and thermal rigors of space. Its housing had even been made from gold-plated Kovar, an alloy chosen partly because it expands very little as its temperature changes. Unfortunately, deep inside was an adhesive that wasn't quite so spaceworthy. In a vacuum, the adhesive began to outgas, releasing molecules that accumulated on nearby optical components as a carbon-rich film. In testing, the contamination caused the laser's output to plummet from around 20 milliwatts to just 4 milliwatts over the course of a week. And, by the time the scientists identified the problem, the flight model was already integrated into the Falcon 9. Oops. There was no longer any opportunity to replace the adhesive or clean the contaminated optics. And, just as the testing had predicted, the laser's output continued to decline during operation in space, compounding the dwindling signal from the radiation-battered detectors. Somehow, despite all these really big setbacks, they still managed to get the cockamamie thing to work. In order to perform quantum operations, the photons traveling through the instrument's circuits need to be indistinguishable. If two such photons are sent into opposite sides of the same optical junction at exactly the same time, something distinctly quantum happens. Rather than each taking its own path through the junction, the two photons interfere with one another so they tend to emerge together. This produces what physicists call a Hong-Ou-Mandel dip: as the photons become more alike, the number of times detectors catch them emerging separately suddenly drops. And that's exactly what the researchers saw in space. To put it to the test, the researchers gradually changed the temperature of the crystal producing the photon pairs. This changes the photons' wavelengths, allowing the team to tune them until their spectra match and they become indistinguishable. They knew from tests on Earth that this sweet spot should occur at around 32.5 degrees Celsius. Sure enough, at almost exactly that temperature, the coincidence rate plunged, producing a clear Hong-Ou-Mandel dip.The telltale dip in photon detections as the crystal reached around 32.5 °C revealed quantum interference taking place aboard the satellite. (Steiner et al., arXiv, 2026)Its visibility – essentially a measure of how strongly the photons interfered – was 0.908, above the classical limit of 0.5, although the considerable uncertainty in the measurement meant the result cleared that threshold by 2.14 standard deviations. But the researchers also reproduced the dip independently on two different days, and when they deliberately reconfigured the processor into a state that should not produce the effect, the dip disappeared. In spite of its technical issues, the team's instrument was generating and manipulating the non-classical interference on which photonic quantum computing relies. Can it process satellite data? Very much not yet. But the processor represents a critical test that will allow researchers to refine their designs and build more robust instruments for the orbital environment. "The results reported here are the first step along this path we are pursuing, to allow for classification and compression on the photonic hardware itself, while sending only the inference product to the ground," the researchers write. "This progress would make orbiting processors the natural counterpart to the quantum links already established between satellites and the ground: nodes and channels together define a distributed architecture with global coverage and low-latency access, in which quantum computation is no longer confined to controlled laboratory environments but deployed at scale across the network."The paper, yet to be peer-reviewed, is available on preprint server arXiv. This article was fact-checked by Peter Dockrill and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.