30 Times More Precise: Antimatter Positron Trapped for Months

Physicists at Northwestern University kept a single antimatter particle confined in a vacuum chamber for months, a feat that let them probe its quantum behavior with roughly 30 times the precision scientists had previously achieved, according to the American Physical Society, Wired reported. The work, led by physicist Gerald Gabrielse and published in Physical Review Letters, targets one of the oldest open questions in physics: whether matter and antimatter are truly mirror images of each other.

How Researchers Trapped a Single Positron for Months

The team built a device called a single-positron quantum cyclotron, which uses electric and magnetic fields to hold a positron, the antimatter counterpart of the electron, inside a vacuum chamber, Wired reported. Cooling the particle to temperatures near absolute zero pushed it into its lowest possible energy state, giving researchers fine control over its quantum states without physically touching it, according to the outlet's account of the Physical Review Letters paper.

That combination of isolation and extreme cold is what let the positron survive, trapped and intact, for months rather than the fractions of a second typical in many antimatter experiments, Wired reported.

Why Antimatter Particles Are So Hard to Study

Antimatter is notoriously difficult to work with because contact with ordinary matter triggers annihilation, releasing energy and destroying both particles instantly, according to Wired. Laboratories that produce antimatter rely on vacuum chambers and electromagnetic fields to keep antiparticles isolated from any surface or stray matter that would wipe them out.

Even with that isolation, Wired reported, studying the particles' behavior at the quantum level has remained an unresolved challenge, since most techniques either destroy the particle during measurement or cannot hold it long enough to repeat an experiment.

What the Northwestern Device Does Differently

Unlike conventional particle-physics methods that consume the antiparticle during measurement, the Northwestern approach left the trapped positron intact, according to Wired's reporting on the study. That non-destructive design allowed the same single antimatter particle to be measured repeatedly over months, a capability the outlet described as central to the experiment's design.

The new device could enable measurements of antimatter particles about 30 times more precise than scientists were capable of before, according to the American Physical Society.

Repeat measurements on one particle, rather than one-shot measurements on many, give researchers a way to average out noise and tighten uncertainty, which is the basis for the APS's precision estimate cited by Wired.

Why the Matter-Antimatter Imbalance Still Puzzles Physicists

The standard model of particle physics predicts that every particle of matter has a corresponding antiparticle, and experiments have confirmed that pairing, Wired reported. By that logic, the universe should contain roughly equal amounts of matter and antimatter. Instead, nearly everything observable is ordinary matter, and physicists still do not know why, according to the outlet.

One path toward an answer is checking whether particles and their antiparticles are identical in every respect except charge. An electron and a positron have the same mass but opposite electric charge, Wired noted, and physicists have already measured electrons' magnetic properties with high precision. Matching that precision for positrons has proven far harder, which is the gap the Northwestern device is built to close.

What the 30-Fold Precision Gain Could Reveal Next

Comparing the magnetic properties of positrons against the long-established measurements for electrons is the next step researchers described to Wired. If a measurable difference ever turns up, it could point toward physics beyond the standard model and help explain why matter so overwhelmingly outnumbers antimatter in the observable universe.

So far, Wired reported, the experiment has not turned up any unexpected result, meaning the positron's measured properties continue to match theoretical expectations. But the ability to hold and repeatedly probe a single antimatter particle for months, rather than destroying it on contact, gives physicists a tool to keep testing that question with far greater precision than before.