Dephasing and thermal smearing in an electromechanical which-path device

In an electromechanical which-path device electrons travelling through an Aharonov– Bohm ring with a quantum dot in one of the arms are dephased by an interaction with the fundamental flexural mode of a radio-frequency cantilever, leading to a reduction in the visibility of interference fringes. However, at finite temperatures time-averaged measurement of the current leads to a fringe visibility which is reduced partly by dephasing of the electrons and partly by a thermal smearing effect. The balance between the thermal smearing and dephasing predicted by a calculation depends very strongly on the choice of cantilever basis states used. The interaction between the cantilever and its environment is expected to select the coherent state basis for the cantilever and hence lead to a dephasing rate which is substantially lower than that which would arise if instead the Fock states were selected.