We compute the interference pattern of a Mach-Zehnder interferometer operating in the fractional quantum Hall effect. Our theoretical proposal is inspired by a remarkable experimental realization of such an interferometer with edge states in the Integer Quantum Hall effect (IQHE). The Luttinger liquid model is solved via two independent methods: refermionization at $\nu =1∕2$ and the Bethe ansatz solution available for Laughlin fractions. The current differs strongly from that of single electrons in the strong backscattering regime. The Fano factor is periodic in the flux, and at $\nu =1∕2$ it exhibits a sharp transition from sub-Poissonian (charge $e∕2$) to Poissonian (charge $e$) in the neighborhood of destructive interferences. Implications for Laughlin fractions are discussed.

• Received 25 March 2005

DOI:https://doi.org/10.1103/PhysRevB.72.201305