Dynamic Interference of Chirped Photoelectrons

In quantum mechanics, particles like electrons behave as waves and can interfere with themselves. Such interference is well established in space, but what if we could control it in time?

In this study, published on Physical Review Letters, a team of researchers developed a novel technique—chirped laser-assisted dynamic interference—to manipulate temporal quantum interference during photoionization.

By using extreme-ultraviolet pulses with time-varying central frequency, in combination with intense infrared laser fields, they guided electron motion with unprecedented precision.

Careful tuning of the pulse timing and intensity enabled the researchers to control the photoemission process such that electrons emitted at different times reached the same final energy, allowing their quantum trajectories to interfere coherently.

This interference gave rise to well-defined fringe patterns in the photoelectron spectra, revealing key information about the underlying ultrafast dynamics.

These findings, supported by advanced simulations and experiments at the ELI ALPS, a leading European facility dedicated to ultrafast science, represent the first clear experimental observation of this elusive phenomenon, long theorized but previously obscured by competing effects.

The study is the result of a close collaboration between researchers at Politecnico di Milano, Lund University, IFN-CNR, ETH Zürich and ELI ALPS.

Offering deeper insight into how matter responds to strong light fields at the quantum level, this breakthrough gives researchers a powerful new tool to manipulate the behaviour of electrons on attosecond timescales (a billionth of a billionth of a second), unlocking new possibilities for quantum technologies and ultrafast electronics.