Researchers from Israel's Weizmann Institute of Science and Japan's National Institute for Materials Science have reported an Aharonov–Bohm interferometer in bilayer graphene, using it to reveal non-Abelian anyons whose collective quantum state can remember the history of their exchanges - a crucial resource for topological quantum computing.
In this work, ultraclean bilayer graphene is tuned into an even‑denominator fractional quantum Hall state, where strongly interacting electrons in a two‑dimensional carbon lattice fractionalize into anyons with unusual charge and statistics. The device geometry forces an anyonic excitation to travel along a loop around an island containing other anyons and magnetic flux, so that Aharonov–Bohm interference in the encircling wave function shows up directly as oscillations between high and low electrical resistance.
By sweeping the magnetic field, the team first mapped out pure Aharonov–Bohm oscillations, demonstrating that the bilayer graphene interferometer cleanly tracks the phase winding of the orbiting anyon wave as it accumulates flux. They then varied the carrier density inside the island and analyzed how the interference pattern “fans” in resistance shifted, extracting the effective fractional charge and statistical properties of both the orbiting and island quasiparticles.
The measurements reveal an encircling excitation with an effective charge of one‑half of an electron, an unexpected result given the long‑standing theoretical expectation of quarter‑charge carriers for non‑Abelian states.
Complementary analysis and earlier tunneling data indicate that this half‑charge signal arises from a bound pair of non‑Abelian anyons circling the island, while the internal quasiparticles themselves carry one‑quarter of an electron’s charge, as inferred from changes in the interference line slopes.
This graphene‑based Aharonov–Bohm interferometer therefore provides strong evidence that bilayer graphene hosts an even‑denominator, non‑Abelian fractional quantum Hall phase, accessed and controlled in a wafer‑scale, carbon platform. Because non‑Abelian anyons store information nonlocally in the global wave function—so that different braiding histories imprint distinct, robust signatures - this bilayer graphene system emerges as a promising solid‑state route toward fault‑tolerant, topological qubits and quantum processors.
