ERASING the past is now easier thanks to the latest 鈥渢ime cloak鈥�, which conceals events instead of objects. The device can鈥檛 cloak large-scale events such as a bank robbery but it can hide data flowing through an optical fibre, which could allow secret messages to be sent without a trace.
鈥淚n a sense we鈥檙e erasing this data from history,鈥� says Joseph Lukens at Purdue University in Lafayette, Indiana. Time cloaks work by slowing down light in an optical fibre, creating a gap in the beam. Any outside light that enters the hole becomes cloaked when the original beam is sped up. It鈥檚 as if the original beam has been stitched back together like a spliced movie, hiding any record that the extra scene ever happened.
Last year researchers at Cornell University in Ithaca, New York, demonstrated the first working time cloak via a gap lasting 40 trillionths of a second. But that could only hide a small blip of information. Now Lukens and colleagues have created a series of time cloaks in quick succession, allowing much more information to be cloaked. A diffraction grating stretches out a laser beam, producing a series of gaps. Pulses of light sent along the fibre at the same time slot into these. A second grating then closes the holes, hiding the pulses from the intended receiver. There is now no record that the pulses ever traversed the fibre (). This string of cloaks can hide up to 1.5 gigabytes per second. 鈥淲e鈥檙e able to actually cloak real-world data,鈥� says Lukens.
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聯The 鈥榯ime cloak鈥� can hide up to 1.5 gigabytes per second, enough to cloak real-world data聰
That might be useful for securing communications, but only once the data can be uncloaked at the other end to read the message. Until then, the cloaks could be used to block nefarious messages. of Imperial College London, who helped dream up the idea of a time cloak in 2010, says a stream of cloaks is an interesting twist on the notion of concealing one event.
This article appeared in print under the headline 鈥淭ime cloak deletes chunks of history鈥�
