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Physicists Hold Single Antimatter Particle for Months and Control Its Quantum States
· Confirmed
In Short: Physicists at Northwestern University have held a single positron, the antimatter counterpart of an electron, in a trap for months, marking a significant step in antimatter research.
According to the Standard Model of particle physics, electrons and positrons should be nearly perfect mirror images of one another.
The team responsible describes the condition in which their particle was held as a 'one-positron quantum cyclotron,' providing an unprecedented opportunity to study antimatter's behavior.
Gabrielse, the senior author of the paper, said, 'Antimatter gets its popular charm from science fiction.' He added, 'To be clear, it’s not dangerous.'
The magnetic moment measurement is just one of many realms where physicists are seeking differences between matter and antimatter to account for this profound discrepancy.
The advance ultimately could enable the most precise test yet of a fundamental symmetry between electrons and their antimatter counterparts.
For this experiment, the team captured a positron produced by the radioactive decay of sodium-22 and suspended it in electric and magnetic fields for months, preventing destructive contact with ordinary matter.
Loading one antimatter particle into the trap takes up to 11 hours.
Using tuned microwave pulses, they triggered and observed single jumps between cyclotron levels and single flips of the particle’s spin.
The 2023 electron measurement showed how far that approach can reach, and a matching positron result would turn it into the sharpest test of CPT symmetry for this family of particles.
Gabrielse noted, 'We know the Standard Model has to be wrong somewhere — or at least incomplete.'
Finding a mismatch in measurements between matter and antimatter 'would be revolutionary in physics', says Gabrielse.
The biggest challenge is to persuade a positron that is ejected from a nucleus in a radioactive decay with a very high energy to slow down enough that we can capture it into our particle trap.
Background
Physicists at Northwestern University have held a single positron, the antimatter counterpart of an electron, in a trap for months, marking a significant step in antimatter research.
What's confirmed
- “Antimatter gets its popular charm from science fiction,” Gabrielse said in a statement.
- The team responsible describes the condition in which their particle was held as a “one-positron quantum cyclotron”, providing an unprecedented opportunity to study antimatter’s behavior.
- According to the Standard Model of particle physics, electrons and positrons should be nearly perfect mirror images of one another.
- By trapping and cooling a positron this way, the scientists created what they call a “one-positron quantum cyclotron.” In this state, the positron essentially behaves much like an artificial atom with quantum energy levels scientists can precisely control and observe.
- The advance ultimately could enable the most precise test yet of a fundamental symmetry between electrons and their antimatter counterparts.
- Physicists at Northwestern University have held a single positron — the antimatter twin of the electron — in a trap for months and manipulated it one quantum jump at a time.
- According to our best theories, the Big Bang should have created equal amounts of matter and antimatter.
- The Northwestern team described its achievement in controlling a positron, the antimatter counterpart of an electron, in a recent paper published in Physical Review Letters.
- Their corresponding particles have identical masses and opposite electric charges, but previous experiments have revealed subtle differences in how certain particles and antiparticles decay, a phenomenon known as charge-parity violation (CP violation).
- “Current theories suggest that there will be no difference in the two measurements,” Gabrielse said.
- “We know the Standard Model has to be wrong somewhere — or at least incomplete,” Gabrielse said.
- For a positron, the antimatter counterpart of an electron, even touching the walls of a container would mean instant destruction.
What's still developing
- They have observed a slight preference for matter in the behaviours of a handful of particles, but nowhere near enough to account for the world’s composition.
- They call their setup a ‘one-positron quantum cyclotron.’ Cloud chamber photograph by the American experimental physicist Carl David Anderson of the first positron ever identified.
- "They end up 'annihilating' with an electron in our apparatus."
- To build their trap, physicists started with atoms of sodium 22, a radioactive isotope with a half-life of about two and a half years.
- Further investigations using the trap might reveal the secret of why the world around us is made of matter and not antimatter, when things could have presumably gone either way.
- But it lasted a remarkable 50 seconds, the longest coherent quantum state ever observed in antimatter.
- Nevertheless, a team led by Professor Gerald Gabrielse of Northwestern University were able to “tame” a positron released during sodium-22 decay and keep it indefinitely for study.
- As with all antimatter particles, on encountering their matter counterpart they annihilate each other, releasing energy equal to the mass of both multiplied by the speed of light squared.
- A positron has been trapped and held captive at a temperature close to absolute zero for a period of months, marking a significant step forward in antimatter control.
- They would have spewed out energetic particles — a phenomenon called Hawking radiation — thereby heating their surroundings.
- Shock waves in the early universe may have helped matter reign supreme Primordial black holes (illustrated) could explain how the universe came to be formed predominantly from matter, while antimatter is rare.