Quantum computers are very fragile devices, the accidental observation of any quantum property can disrupt calculations before they have been completed. ¿Could a quantum computer be hidden inside a protecting spatiotemporal cloaking device? Such is the proposal of Ortwin Hess, a researcher into metamaterials at the University of Surrey in Guildford, UK, after reading the theoretical paper of Martin W. McCall (Imperial College of London, UK) and colleagues. A hole carved out of space–time can be made using metamaterials, substances with a complex internal structure that allows them to channel light around objects like water flowing around a rock in a river. The refractive index, the optical property that governs the speed of light within a material, continually changes, pulling light rays apart in time; when the leading edge of a light wave hits the cloak, the material is manipulated to speed up the light, but when the trailing edge hits, the light is slowed down and delayed. Between these two parts of the light, there will be a temporal void, a space in which there will be no illuminating light for a brief period of time. The figure above, from the original paper, explain the idea with a spatiotemporal diagram.
The technical paper is Martin W. McCall, Alberto Favaro, Paul Kinsler, Allan Boardman, “A spacetime cloak, or a history editor,” Journal of Optics 13: 024003, 16 November 2010 [the access is free during this month, after free registration]. Further nontechnical information in Zeeya Merali, “Space–time cloak could hide events. Proposed device could edit actions out of history,” News, Nature, Published online 16 November 2010, and “Spacetime cloak to conceal events revealed in new study,” Nanowerk News, Nov 16th, 2010 [the last article includes an animation explaining the idea using cars in a highway].
In relation with optical cloaking devices, I recommend the recent paper by, obviously, John Brian Pendry et al. (the figure below is for motivation purposes): Yaroslav A Urzhumov, Nathan B Kundtz, David R Smith, John B Pendry, ”Cross-section comparisons of cloaks designed by transformation optical and optical conformal mapping approaches,” Journal of Optics, 13: 024002, 16 November 2010.