Relaxation and revival of quasiparticles injected in an interacting quantum Hall liquid.

The one-dimensional, chiral edge channels of the quantum Hall effect are a promising platform in which to implement electron quantum optics experiments; however, Coulomb interactions between edge channels are a major source of decoherence and energy relaxation. It is therefore of large interest to understand the range and limitations of the simple quantum electron optics picture. Here we confirm experimentally for the first time the predicted relaxation and revival of electrons injected at finite energy into an edge channel. The observed decay of the injected electrons is reproduced theoretically within a Tomonaga-Luttinger liquid framework, including an important dissipation towards external degrees of freedom. This gives us a quantitative empirical understanding of the strength of the interaction and the dissipation. Quantum Hall phases have chiral edge modes, which could be used to explore and exploit the quantum properties of electrons. Interactions in these edge states lead to relaxation and decoherence, hindering any realistic exploitation. Here the authors observe spectroscopically the decay and revival of the excitation created by injection of an electron into the edge mode. Their results confirm phase-coherent transport and quantify the effect of dissipation-induced decoherence.