  We investigate the time-evolution of a charge qubit subject to quantum
telegraph noise produced by a single electronic defect level. We obtain results
for the time-evolution of the coherence that are strikingly different from the
usual case of a harmonic oscillator bath (Gaussian noise). When the coupling
strength crosses a certain temperature-dependent threshold, we observe
coherence oscillations in the strong-coupling regime. Moreover, we present the
time-evolution of the echo signal in a spin-echo experiment. Our analysis
relies on a numerical evaluation of the exact solution for the density matrix
of the qubit.
