Larger charge produces louder noise; smaller charge produces quieter noise. Comparing the measured noise against known reference states lets researchers back out the unknown charge.

To check their setup, the team first measured two reference states with well-known charges — one full electron, and one with two-thirds of an electron's charge (2e/3). Both came out as expected.

What did they find in the ν = 1/2 state?

When they turned the technique on the ν = 1/2 state, two devices — one at EPFL, one at Weizmann — gave matching answers: 0.250 ± 0.013 and 0.249 ± 0.018 times the electron charge. Both numbers match e/4, a quarter of an electron.

The agreement is what makes the result notable. Until now, claims of fractional charges in even-denominator states had been hard to verify, because few labs could reproduce the exact conditions. Two measurements from two separate labs converging on the same value strengthen the case.

Why does a quarter-electron matter?

The ν = 1/2 state belongs to a small group of even-denominator fractional quantum Hall states. Most such states are predicted to host unusual quasiparticles called "non-Abelian anyons." These particles carry quantum properties that change in a predictable way when two of them swap positions.

That history-dependence is exactly what makes them attractive for a particular kind of quantum computer. In a "topological" quantum computer, information would live not in individual particles but in the global pattern of how non-Abelian anyons have been braided — that is, exchanged in space. Local noise and defects cannot easily corrupt such information, because the data sits in the overall geometry rather than at any single point.

Banerjee summed up the appeal: "Non-Abelian states act like a structural blueprint, where information is stored in the global geometry rather than a single point, ensuring immunity from local structural defects or noise. By simply moving such particles around each other, we can create error-free quantum computers."

How robust is this state?

Most quantum Hall states demand temperatures within a hair of absolute zero. The ν = 1/2 state is unusual because it survives at temperatures "up to a few kelvins," Banerjee noted — still cold by everyday standards, but thousands of times warmer than the millikelvin regime typical for these experiments.

"This is important because the quantum Hall state that was studied here is special as it survives up to a few kelvins, and is thought to be only the second known state in gallium arsenide to possess special non-Abelian properties that can eventually enable a topological quantum computer," she said.

What still needs to be shown?

Charge is one signature of non-Abelian anyons. The full test is to demonstrate that the quasiparticles behave as proper non-Abelians — meaning that their quantum state changes in a predictable way when two of them swap positions in space. That braiding experiment has not yet been done for the ν = 1/2 state.

Other labs will likely attempt to reproduce the shot-noise measurement in additional devices. Each confirmation tightens the case that quarter-charge quasiparticles in gallium arsenide are real, and stable enough to manipulate in future quantum hardware.