For the first time, physicists at CERN have coaxed an antiproton — a mirror twin of the matter that makes up our world — into behaving like a quantum bit, or qubit. The antiproton held its quantum balance, hovering between spin states, not for a fraction of a second, but for a full 50 seconds.
This peculiar feat achieved by the BASE collaboration at CERN, represents a deliberate, delicate step into the deeper questions of the universe, toward the unsettling puzzle of why anything exists at all.
The First Quantum Bit of Antimatter
At the heart of the experiment is a question that still haunts physicists: why does the universe consist almost entirely of matter? According to theory, the Big Bang should have created equal amounts of matter and antimatter. When matter and antimatter meet, they annihilate in a burst of energy — so if they had been created in perfect balance, the universe should have quickly destroyed itself.
And yet, here we are.
To investigate this puzzle, researchers have long looked for tiny differences between matter and antimatter. The BASE team specializes in ultra-precise measurements of the magnetic moment of the antiproton, a property that acts like a tiny bar magnet aligned with the particle’s spin. Comparing this value to that of the proton could reveal cracks in what’s known as CPT symmetry — the idea that the laws of physics are the same for particles and antiparticles.
So far, those measurements have found no differences. But now, using techniques typically reserved for quantum computing, the BASE team has opened a new path: coherent quantum transition spectroscopy on a single trapped antiproton spin.
The 50-Second Quantum Balancing Act
To create the antimatter qubit, researchers placed a single antiproton inside a cryogenic Penning trap, using precisely tuned magnetic and electric fields to hold it steady in isolation. Then, they applied a carefully calibrated pulse of radiofrequency energy to place the antiproton’s spin into superposition — a quantum state where it is simultaneously “up” and “down.”
This bizarre dual existence didn’t last forever. Eventually, the quantum state collapsed as decoherence set in. But it lasted a remarkable 50 seconds, the longest coherent quantum state ever observed in antimatter.
“This represents the first antimatter qubit and opens up the prospect of applying the entire set of coherent spectroscopy methods to single matter and antimatter systems in precision experiments,” said Stefan Ulmer, spokesperson for BASE and physicist at RIKEN and CERN.
The team observed distinct Rabi oscillations — periodic changes in the spin direction — as they varied the drive time. These oscillations are the hallmark of a well-behaved qubit and offer a way to measure the magnetic moment with unprecedented accuracy.
According to their published results, the precision trap achieved transition linewidths up to 16 times narrower than in previous measurements, with spin inversion probabilities as high as 80%.
Not for Computing — Yet
Unlike silicon-based qubits used in experimental quantum computers, antimatter qubits are unlikely to find real-world computing applications any time soon. The engineering challenges are immense: creating, storing, and isolating antimatter requires facilities like CERN’s Antiproton Decelerator and technology that prevents matter-antimatter annihilation.
“It does not make sense to use [the antimatter qubit] at the moment for quantum computers,” said Barbara Latacz, CERN physicist and lead author of the study. “Engineering related to production and storage of antimatter is much more difficult than for normal matter.”
Still, the theoretical implications are significant. If future experiments find any discrepancy between how matter and antimatter behave — even at a quantum level — it could be a clue to the universe’s imbalance. “If you are just looking into the physics, there’s absolutely no reason why there should be more matter than antimatter,” Ulmer explained to Scientific American.
Future of Antimatter Research
The current experiment was conducted at CERN’s accelerator complex, which introduces fluctuating magnetic fields that can disturb sensitive measurements. That’s why the next phase of the project involves BASE-STEP (Symmetry Tests in Experiments with Portable Antiprotons), a transportable trap system designed to ferry antiprotons to quieter labs.
“Once it is fully operational, our new offline precision Penning trap system, which will be supplied with antiprotons transported by BASE-STEP, could allow us to achieve spin coherence times maybe even ten times longer than in current experiments,” Latacz told Space.com.
Such a setup could enable 10- to 100-fold improvement in precision when measuring the antiproton’s magnetic moment. The goal is to reach sensitivities of 10 parts per trillion — precision so high it could expose subtle asymmetries hidden beneath the apparent balance of matter and antimatter.
A Subatomic Mirror
So far, every experiment probing matter-antimatter symmetry has reinforced the idea that the two are nearly indistinguishable. Previous BASE measurements found the magnetic moments of protons and antiprotons matched to within 1.5 parts per billion.
But the improved resolution of coherent spectroscopy raises hopes for a breakthrough.
This work “could be interesting to do basically the same calculations with matter qubits and antimatter qubits and compare the results,” said Ulmer. That comparison might someday point to a fundamental asymmetry responsible for the imbalance that shaped the cosmos.
And although the antimatter qubit won’t help build warp drives or quantum computers just yet, it is a powerful tool in a different quest: understanding why the universe exists in the first place.
Even if the antimatter qubit doesn’t crack the asymmetry enigma today, it’s moving us closer to the day we might.
The findings appeared in the journal Nature.
