Topological phases are like a knot on a thread: you look at a small piece, and the knot isn't visible. Previously, to find such hidden order in a material, you had to measure the entire sample. But the quantum world works differently: thanks to the ability of particles to be in multiple states at once, even a tiny region carries information about the whole, like a hologram in every fragment.

Researchers took advantage of this. They trained a computer program on calculations of small systems to decode this 'quantum fingerprint'—a concept introduced by von Neumann and called the reduced density matrix. Now, by looking at just a few atoms, the algorithm guesses the phase type.

The method eliminates bulky measurements on entire systems. It speeds up the creation of stable quantum devices and confirms the hunch of Landau that order can mask itself — until clever analysis exposes it.