  Recent double-slit interference experiments have demonstrated the possibility
of probing the phase of the complex transmission coefficient of a quantum dot
via the Aharonov-Bohm effect. We propose an extension of these experiments: an
ac voltage imposed on the side gate with the concomitant photonic sidebands
leads to additional structure both in the amplitude and in the phase of the
Aharonov-Bohm signal. Observation of these effects would be a definitive proof
of coherent absorption and reemission of photons from the ac source.
