Capturing the Void: Physicists Sustain a Single Antimatter Particle for One Month

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By Clara Moskowitz | Edited by Lee Billings Originally published October 21, 2026

In a landmark achievement for quantum physics, researchers have successfully isolated a single positron—the antimatter twin of the electron—for a duration of one month. This breakthrough allows scientists to perform unprecedented quantum measurements on antimatter, potentially unlocking the mystery of why our universe is composed of matter rather than a void of annihilation.

The Fundamental Conflict

The primary obstacle in studying antimatter is its volatile nature. You cannot simply hold antimatter in your hand or store it in a standard glass jar.

"If you want to hold on to antimatter, you have to hold it in a container without walls," explains Gerald Gabrielse, a physicist at Northwestern University who led the study.

As soon as matter and antimatter collide, they undergo annihilation, converting their mass entirely into energy.

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The Engineering of the Trap

To achieve this feat, reported in Physical Review Letters, the team developed a sophisticated multi-stage capture process.

Experimental Workflow

• Source Generation: Utilize atoms of sodium-22 ($^{22}\text{Na}$), a radioactive isotope with a half-life of $\approx 2.5$ years.
• Emission: Capture the positrons released during the decay of these atoms.
• Deceleration: Pass particles through a cold tungsten crystal lattice to bleed off energy.
• Guidance: Use electromagnetic fields to steer the slowed particles.
• Isolation: Lock the particle in a vacuum.

The final trapping environment is extreme: a vacuum maintained at just $0.3^\circ\text{C}$ above absolute zero. The particle is suspended by a combination of electric fields (top and bottom) and magnetic fields (sides).

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The Scientific Objective: The Magnetic Moment

The team's goal is to measure the positron's magnetic moment—essentially the orientation and strength of its internal magnetic field. To calculate this, they must determine:

1. The energy required to flip the particle's spin.
2. The energy needed to transition the particle from its ground state to its first excited state.

Comparative Analysis

The researchers are comparing the positron's properties against those of the electron, which they have already measured with staggering precision.

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Why This Matters: The Cosmic Imbalance

According to the Standard Model of particle physics, the positron should have a magnetic moment exactly opposite to that of the electron. However, if a discrepancy is found, it could explain the "Great Asymmetry" of the Big Bang.

Theoretically, the early universe should have produced equal amounts of matter and antimatter. While most annihilated, a tiny surplus of matter remained to form the stars and planets. Roni Harnik, a theoretical physicist at Fermi National Accelerator Laboratory, describes the symmetry test as follows:

def test_universe_symmetry(particle):
    # CPT Symmetry: Charge, Parity, and Time
    flip_charge(particle)
    mirror_physics(particle)
    reverse_time_flow(particle)
    
    if particle.magnetic_moment != electron.magnetic_moment:
        return "Clue found: Matter won the cosmic battle!"
    else:
        return "Symmetry holds: Mystery continues."

If the positron deviates from the electron's properties, physicists will finally have a hint as to why matter dominated the cosmos.