Mirrors Switch, the Force Does Not
Davide Iannuzzi, Mariangela Lisanti, and Federico Capasso

The Casimir force is the attraction between two uncharged surfaces arising from quantum fluctuations of the electromagnetic field. We have measured the Casimir force using Hydrogen Switchable Mirrors (HSM), shiny metals that become transparent when exposed to hydrogen. On intuitive grounds, the force in air should be larger than that in hydrogen due to the reduced reflectivity of the mirror. On the contrary, we did not observe any change upon hydrogenation. This counterintuitive finding can be explained by an elusive property of the theory (D. Iannuzzi, M. Lisanti, and F. Capasso, Proc. Nat. Ac. Sci. USA 101, 419 (2004))