Anyonic Braiding in a Chiral Mach-Zehnder Interferometer

Fractional quantum statistics are a signature prediction of fractional quantum Hall states, which have long been elusive in experiments. Here, we present the observation of anyonic interference and exchange phases in a novel co-propagating 'optical-like' Mach-Zehnder Interferometer. This architecture is free of charging and backscattering effects that often plague the widely used Fabry-Perot interferometer, thus exhibiting pristine Aharonov-Bohm (AB) interference without fractional phase slips. We studied the three lowest Jain filling factors, ν=1/3, 2/5, and 3/7, which host quasiparticles with fractional charges e^*=e/3, e/5, and e/7, respectively. The observed AB interference patterns, plotted as a function of magnetic field B and modulation-gate voltage, V_MG (known as pajamas), exhibited the expected flux periodicities: 3Φ₀, 5Φ₀, and 7Φ₀, with Φ₀ being the flux quantum. A small biased top gate (TG) deposited in the center of the interferometer induces local quasiparticles that are spatially isolated from the interfering modes. At non-zero TG voltage V_TG, quantized phase slips appear in the AB pajamas approximately with every flux quantum that pierces the effective area below the TG. Moreover, when tuning V_TG, at a constant magnetic field, abrupt phase jumps corresponding to adding one localized quasiparticle at a time under the top gate appear in the B-V_TGpajamas.