In a chain of eight spins, a defect lurks — a tiny magnetic moment. The Kondo effect, known since the 1930s, makes electrons around it align into a collective screen. The material's resistance abnormally increases. But detecting such an impurity hidden deep in the structure is like finding a stone at the bottom of a dark pond. Physicists found a way: by the ripples on the water.

Two observers, Alice and Bob, are far from the defect and from each other. The entire chain is permeated by quantum entanglement — a nonlocal connection like a taut net of threads between atoms. Alice introduces a disturbance: she measures the spin of her atom at point 4. It's like tossing a pebble into a pond — a local action instantly changes the entire entanglement pattern. She sends the measurement result to Bob via an ordinary communication channel. Upon receiving the signal, Bob applies an operation to his atom (point 7) depending on the result, and then measures the energy. The entire process is described by the Schrödinger equation and simulated numerically by exact diagonalization.

The energy Bob extracted turns out to be remarkably informative. It precisely replicates the system's phase diagram, usually calculated through entanglement entropy. Where entropy peaks, the teleported energy also peaks.

Moreover, the condensations in the entanglement spectrum clearly indicate a phase transition, and the energy response picks them up.

Thus, quantum energy teleportation becomes an echo-sounder tool. It allows probing hidden defects and quantum phases without direct contact. This is crucial for quality control of future materials: from spintronic devices to protected qubits in quantum computers.

The immediate goal is to hear this echo in the lab. Scientists plan to assemble a chain of Rydberg atoms held in an optical lattice, where interactions mimic exchange constants. The stone remains invisible, but the circles on the water reveal its location and mass. We just need to learn to read those ripples without error.