'Schrödinger's Hat' Uses Invisibility to Measure Quantum World: Mathematicians now suspect quirks in energy-cloaking metamaterials could be exploited to create powerful quantum probes called "Schrödinger's hats." Such probes might record extremely subtle signals that would otherwise be scrambled by any attempt to measure them.
Yet no ideal metamaterials exist. All slightly betray the existence of objects they conceal, and none completely divert a wide range of energetic frequencies. Some metamaterials even resonate like tuning forks at specific frequencies, sounding like an alarm instead of hiding something.
Where some scientists see flaws, however, Greenleaf and his colleagues see opportunity. If the amount of energy going through a metamaterial and the amount of energy coming out are almost perfectly balanced, the resonating metamaterial should trap a signal that describes the environment it was just in. Over time the signal would leak out, allowing researchers to record it.