Fractional quantum Hall effect in a quantum point contact at filling fraction 5/2

Recent theories suggest that the quasiparticles that populate certain quantum Hall states should exhibit exotic braiding statistics that could be used to build topological quantum gates. Confined systems that support such states at a filling fraction nu = 5/2 are of particular interest for testing these predictions. Here, we report transport measurements of just such a system, which consists of a quantum point contact (QPC) in a two-dimensional GaAs/AlGaAs electron gas that itself exhibits a well-developed fractional quantum Hall effect at a bulk filling fraction nu(bulk) = 5/2. We observe plateau-like features at an effective filling fraction of nu(QPC) = 5/2 for lithographic contact widths of 1.2 mu m and 0.8 mu m, but not 0.5 mu m. Transport near nu(QPC) = 5/2 in the QPCs is consistent with a picture of chiral Luttinger-liquid edge states with inter-edge tunnelling, suggesting that an incompressible state at nu(QPC) = 5/2 forms in this confined geometry.