Using quantum phase transitions to make better measurement devices

Near a quantum phase transition, systems become exquisitely sensitive to tiny perturbations — a property useful for precision measurement. This work shows that instead of encoding the quantity you want to measure directly in a critical Hamiltonian (which limits what you can measure and over what range), you can use critical evolution just to prepare the probe state, then measure something else entirely. The resulting mismatch between preparation and encoding — quantified by a quantity called skew information — amplifies the quantum Fisher information, the gold standard for measurement precision, at no extra time or energy cost.