Motivated by the recently developed theory of photon-assisted quantum
transport, we have studied transport properties of an antenna-coupled
quantum point contract under coherent far-infrared (285 GHz) radiation
. A pronounced photon-induced drain/source current is observed. The am
plitude of the photon-induced current is about 10% of that correspondi
ng to a quantized conductance step, and it oscillates with the gate vo
ltage. Our analysis suggests that the observed photon-induced current
is mainly due to heating of the electron gas in the source and drain (
a bolometric effect) rather than photon-assisted quantum transport. Fu
ture improvement of the device parameters to enhance the effect of pho
ton-assisted transport will be discussed.