Unexpected finite-bias visibility dependence in an electronic Mach   Zehnder interferometer
  We use an electronic Mach-Zehnder interferometer to explore the non-equilibrium coherence of the electron waves within the edge-states that form in the integral quantum Hall effect. The visibility of the interference as a function of bias-voltage and transmission probabilities of the mirrors, which are realized by quantum point-contacts, reveal an unexpected asymmetry at finite bias when the transmission probability $T$ of the mirror at the input of the interferometer is varied between 0 and 100%, while the transmission probability of the other mirror at the output is kept fixed. This can lead to the surprising result of an increasing magnitude of interference with increasing bias-voltage for certain values of $T$. A detailed analysis for various transmission probabilities and different directions of the magnetic field demonstrates that this effect is not related to the transmission characteristics of a single quantum point contact, but is an inherent property of the Mach-Zehnder interferometer with edge-states. 
E. Bieri, M. Weiss, O. Goktas, M. Hauser, S. Csonka, S. Oberholzer, C.   Schonenberger