The quantum world does not forgive forgetfulness. Throw a stone into a pond — the ripples spread and vanish, the information about the impact dissipates without a trace. In quantum mechanics, everything is different: the evolution of a system is reversible, and the past is never completely erased. But how do you tell a system ruled by thermal chaos from one where particles are locked in their own cells and remember the initial state?

The authors of the paper found a way. They mentally 'multiplied' the system's history — took several copies and traced how the forward and backward paths in time relate. In this intricate tangle, a hidden parameter is born — something like an internal clock. Its hand behaves differently in three regimes. In chaos, it freezes, synchronizing over vast distances. In the ordered phase, its motion quickly decays. And at the boundary between them, it changes smoothly, without a characteristic scale.

This approach does not just provide a new classification. It allows a deeper look — distinguishing systems that previously seemed identical. The hidden coordinate arising from 'multiplied' histories captures order where ordinary measures are blind. This is a step toward understanding how the quantum world balances between memory and forgetting.