Real-time Ramsey interferometry in fractional quantum Hall states

We study the time-dependent dynamical phase of fractional quasiparticles in quantum Hall states using Ramsey interferometry. A Ramsey two-pulse voltage modulation generates an interference term in the current noise of a quantum point contact oscillating with the dynamical phase. We show that the interference pattern probes the Green's function of the fractional quasiparticles in the time domain and reveals the fractional charge. We address both the case of a pointlike tunnel junction and the case of momentum-resolved tunneling which also provides information on the speed of those quasiparticles propagating along the edge. For the 5/2 fractional quantum Hall case, the Ramsey signal can reveal the charge e/4 and differentiate between Pfaffian and anti-Pfaffian states.