Theory of excess noise of a quantum dot in the presence of a microwave field

The power spectrum of excess noise of a quantum dot coupled to two leads and irradiated by a microwave field of frequency Omega is derived exactly by directly solving the Heisenberg equation. We found that for Gamma <h Omega, where Gamma is the Linewidth of the intradot energy level, the power spectrum can be nonzero even if the averaged current is zero. This property originates from photon-assisted tunneling and is very different from the shot noise in steady state. For Gamma much greater than h Omega, our results are consistent with the recent experiment by Schoelkopf er nl. and previous theory.Physics, Condensed MatterSCI(E)19ARTICLE1913032-130366