Scientists show how to create 'invisibility cloak' for waves

Mathematicians have determined how to create an invisibility cloak that works for anything that acts like a wave, such as light, sound and particles. The cloak makes the waves inside it impossible to detect from the outside. 

Inside the cloak, the waves can either be amplified or shrunk so they're hidden. "You can isolate and magnify what you want to see and make the rest invisible," said Gunther Uhlmann, a mathematician from the University of Washington who led the study. 

Uhlmann and his colleagues call this unusual state a Schrödinger hat, partly to commemorate the Schrödinger's cat thought experiment, which applies the uncertainty in quantum physics rules to a cat to show how strange quantum physics rules sound when they're applied to a bigger, more everyday example.

The name also refers to how magical the cloak's effects appear to be. "It looks like a particle is being created. It's like pulling something out of your hat," Uhlmann said. In addition, the hat state is expected to work for any waves described by one of two equations, named after Schrödinger and Hermann von Helmholtz, a 19th-century physicist.

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A Schrödinger hat could be used to make a microscope that detects the quantum waves of matter, the researchers wrote in their paper, which was published in Monday's early edition of the Proceedings of the National Academy of Sciences. Such a device would help engineers monitor electronic processes on computer chips. 

Though the mathematicians haven't built a Schrödinger hat device yet, it should be easy to do for sound waves, which are long in comparison to light waves and electromagnetic waves, Uhlmann said. The team is looking for collaborators to help them build a prototype device. 

"We hope that it's feasible, but in science, you don't know until you do it," he said.  

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