Filming the Quantum-to-Macroscopic Transition: Capturing Quantum Wavepacket Dynamics in a Laser Plasma

Harnessing quantum coherences in chemical reactions is a driving force in the development of next-generation science and technology, from tailored material design to sustainable energy conversion. At their core, such reactions originate from collisions between species, where intermolecular interactions govern the redistribution of coherence and energy that ultimately drive chemical transformation. Because these coherences decay on the ultrafast timescale, capturing such dynamics requires a simultaneous combination of high spatial- and ultrafast temporal resolution that current measurement approaches simply cannot provide. Here we present Coherence Lifetime Imaging, a new approach that records two-dimensional, single-shot movies of coherence dynamics at 0.2 THz frame rates, enabling direct observation of ultrafast quantum coherence evolution in transient macroscopic environments. Using a tailored ultrafast pulse train, we generate a coherent rotational wavepacket and track its dynamics, providing an in-situ quantum tracer of the local collisional environment during a laser-induced plasma breakdown event. We reveal highly transient shockwave gradients with elevated chemical reactivity and that enhanced mixing persists hundreds of microseconds following breakdown. This approach provides a new route to quantify and map phase sensitive collisional dynamics in complex, transient systems, linking fundamental quantum interactions to macroscopic chemical quantities.