  We present a method to probe real-time dynamics in quantum mesoscopic systems
using Ramsey interferometry. This allows us to explore the effect of
interactions on quasi-particles in the time domain. We investigate the
dephasing effects of an ohmic environment on an electron-hole pair in a tunnel
junction. We show that dynamical Coulomb blockade phenomena can be observed for
resistances much smaller than the quantum of resistance. Moreover, the
crossover between high and low impedance limits can be probed for a constant
resistance by a proper control of the voltage modulation.
