Harry Potter's Cloak
Gunther Uhlman (University of Washington)
Associated Sites:PIMS University of Washington
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Invisibility has been a subject of human fascination for millenia, from the Greek legend of Perseus versus Medusa to the more recent The Invisible Man, The Invisible Woman, Star Trek and Harry Potter, among many others.
Over the years, there have been occasional scientific prescriptions for invisibility in various settings but the route to cloaking that has received the most attention has been transformation optics (TO). TO takes advantage of the transformation rules for the material properties of electromagnetic materials to design optical devices with customized effects on wave propagation. For the case of invisibility one can design materials that would steer light around a hidden region, returning it to its original path on the far side. Not only would observers be unaware of the contents of the hidden region, they would not even be aware that something was being hidden.
The origin of TO for cloaking is in a paper of Allan Greenleaf, Matti Lassas and Gunther Uhlmann published in 2003 in Mathematics Research Letters. In this article the authors considered the case of electrostatics. Since then there has been considerable interest in the mathematics and physics community on the subject of invisibility and new proposals for devices and special effects have been considered including electromagnetic wormholes, cloaking at a distance, cloaking in space and time, creating artificial black holes, and many others. For a non-technical description of the work of Uhlmann and collaborators, see: http://www.rni.helsinki.fi/~mjl/invisibility_publications.html.
As Science Magazine stated in 2006 in naming cloaking one of the 10 breakthroughs of the year: "...no matter how you look at it the ideas behind invisibility are likely to cast a long shadow"
- G. Uhlman, A. Greenleaf, Y. Kuryalev, M. Lassas Invisibility cloaking and electromagnetic wormholes http://www.rni.helsinki.fi/~mjl/invisibility_publications.html
- A. Greenleaf, Y. Kuryalev, M. Lassas, G. Uhlman Inverse problems and invisibility Bulletin AMS 46 (2009), 55-97.
- A. Greenleaf, Y. Kuryalev, M. Lassas, G. Uhlman Cloaking Devices, Electromagnetic Wormholes, and Transformation Optics SIAM Review 51 (2009)