Even-denominator fractional quantum Hall states (FQHSs) fall outside the standard Laughlin’s and Jain’s odd-denominator hierarchy. They are of intense current interest because they may exhibit non-Abelian topological order and therefore have applications in topological quantum computation. In this Letter, we study the FQHS at filling factor $\nu =1/2$, observed in a two-dimensional electron system confined to a wide GaAs quantum well. Unlike other even-denominator FQHSs, this state is stabilized at the lowest Landau level and has an energy gap about 10 times larger than the widely studied $\nu =5/2$ FQHS. Moreover, a recently observed pair of daughter FQHSs theoretically predicted the parent $\nu =1/2$ FQHS to be a non-Abelian state. Here, we report shot-noise measurements of partitioned quasiparticles at $\nu =1/2$ by an etch-defined quantum point contact (QPC). Our measurements were performed on two nominally identical devices in two independent experimental setups. Analysis of the shot noise in the weak-backscattering regime (of the QPC) reveals quasiparticles with charge $e/4$, consistent with a non-Abelian order, although it does not rule out an Abelian order. These observations provide a clear benchmark for future studies aimed at probing the topological order of the $\nu =1/2$ FQHS and its quasiparticles’ exchange statistics.

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• Charge
• Quantum Hall effect
• Shot noise
• Quantum wells
• Two-dimensional electron gas