This Temporal Laser Cloak Can Hide Things in Time

How long before we're hiding pocket universes?

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Most splashy inventions have science fiction analogues, appearing in film, television or print long before popping up in real life, like: Star Trek‘s medical tri-corderHarry Potter‘s invisibility cloak or The Transformers‘ metamorphosing robot animals. But a cloak that can blink data out of time itself?

Let’s say you want to hide something you’re doing online, like sending a text message or transferring a file to someone. Nowadays you might choose to encrypt that data, but even if someone listening wasn’t able to crack your encryption scheme, there’s still evidence something was sent. The real trick, if you wanted to cover your tracks, would be devising a way to conceal the transmission itself. And if you wanted to be diabolically clever about it, you might make that concealment mechanism time itself. Crazy fourth-dimensional voodoo science, right?

Maybe not. Back in 2010, researchers at Imperial College London suggested it might actually be possible to hide things in time by generating temporally camouflaged moments during which someone could carry out an action unobserved. Their inspiration? The concept behind prototype invisibility cloaks, which can hide objects by using specially crafted materials that warp the electromagnetic spectrum, making it seem as if the light were flowing continuously without encountering the concealed object.

It’s just a hop, skip and a jump from that to hiding events in time, surmised the researchers, suggesting that by temporally separating light waves, then bringing them back together, you might be able to cloak pockets of time. Those pockets might then allow you to secure data transmissions sent over optical fiber (a transmission medium that conveys data using light). “It doesn’t just prevent eavesdroppers from reading your data — they wouldn’t even know there was any data there to hack,” explains Purdue University electrical engineer Joseph Lukens, lead author of a new study just published in science journal Nature.

Sounding appreciably Fringe-esque yet?

This isn’t the first time scientists have fiddled with a time-cloak: In January 2012, Nature published a paper by scientists at Cornell who wrote that “it may be desirable to cloak the occurrence of an event over a finite time period, and the idea of temporal cloaking has been proposed in which the dispersion of the material is manipulated in time, producing a ‘time hole’ in the probe beam to hide the occurrence of the event from the observer.” They then demonstrated how they’d managed to build a working temporal cloak using laser pulses. But as Nature notes, the “windows in time” weren’t open long enough to conceal data “coming in at telecommunication rates.”

Enter Lukens and his colleagues at Purdue, who approached the challenge of temporally concealing data by exploring a phenomenon known as the Talbot effect — named after British inventor Henry Fox Talbot, who in 1836, observed that when light passes through a diffraction grating (a thin, translucent surface with multiple parallel slits cut at regular intervals) it forms an ornate fractal-like pattern reflective of the diffraction grating itself and sometimes referred to as a Talbot carpet (because it looks like an elaborate rug, apparently). One of the takeaways here is that with a Talbot carpet, there’s predictability — the pattern recurs at regular intervals.

According to Lukens, you can create a version of the Talbot effect that’s temporal as well, with regular intervals of zero light intensity; it’s in these zero-intensity stretches that you can then sequester data.

To pull it off, Lukens and his team piped a laser through a device that split it into its component frequencies and alternated voltage to mess with the laser’s timing, causing the frequencies to recombine destructively and create “time holes.” The team then compressed the laser to increase the time windows, at which point it was time to test it by throwing data into the mix. As Nature notes:

The researchers tested the cloak to see if it was operating correctly by inserting a separate encoded data stream into the fibre during the time windows. They then applied two more rounds of phase modulation — to “undo the damage of the first two rounds”, says Lukens — decompressing the energy again and then combining the separated frequencies back into one. They confirmed that a user downstream would pick up the original laser signal alone, as though it had never been disturbed. The cloak successfully hid data added at a rate of 12.7 gigabits per second.

Alas, it seems the cloaking mechanism worked so well that the data was irretrievably hidden: “We erased the data-adding event entirely from history, so there’s no way that data could be sent as a useful message to anyone, even a genuine recipient,” said Lukens. Whoopsie-doodle.

Still, the presumption is that we’re on the cusp of being able to send secret messages using temporal hidey-holes, so, you know, watch out NSA (and other snoopsters), because stuff’s apparently about to get real.

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