Attosecond Transient Interferometry

Abstract Attosecond transient absorption resolves the instantaneous response of a quantum system as it interacts with a laser field, by mapping its sub-cycle dynamics onto the absorption spectrum of attosecond pulses. However, the quantum dynamics are imprinted in both amplitude and phase of the attosecond pulses. Here, we introduce attosecond transient interferometry and measure the transient phase, while following its evolution within the optical cycle. We demonstrate how such phase information enables us to decouple the multiple quantum paths induced in a light-driven atom, isolating their coherent contribution. Recording the phase of each quantum path allows us to trace back their temporal evolution, following both resonant and non-resonant excitations. Attosecond transient interferometry has the potential to reveal the sub-cycle dynamics in more complex systems such as molecules and solids, disentangling the role of multiple quantum paths, resolving their coherent properties and coupling mechanisms.