Science Interferences_plane_waves

Published on June 6th, 2013 | by Michael Ricciardi

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New Laser Cloaking Technology Creates 'Time Holes' – Allows You To 'Erase History' [VIDEO]

June 6th, 2013 by

interference pattern

Interference fringes in overlapping plane waves. Dark stripes here would correspond to ‘time holes’. Note: image is not from the published research (image source)

When Alice went down the rabbit hole, she may have felt that she might never get back (though she did eventually). But some types of information can be sent into a ‘time hole’ and truly never come back.

A team of engineers (Lukens et al) at Purdue University has developing an optical (laser-based) cloaking method that can hide high-speed data streams such as those  transmitted through telecommunication systems. The new method makes possible “ultra-secure message transmission” that side-steps current efforts in quantum cryptography.

Regarding this comparison, Joseph Lukens, an electrical engineer at Purdue University and lead author of the latest study, stated: “It doesn’t just prevent eavesdroppers from reading your data — they wouldn’t even know there was any data there to hack.” [source: see link, below]

Some Background on the Basic Principle

Talbot Effect or 'carpet'

The optical Talbot Effect for monochromatic light, shown as a “Talbot Carpet”. At the bottom of the figure the light can be seen diffracting through a grating, and this exact pattern is reproduced at the top of the picture (one Talbot Length away from the grating). Halfway down you see the image shifted to the side, and at regular fractions of the Talbot Length the sub-images are clearly seen (Ben Goodman, cc-by-sa 3.0)

 

The new cloaking method actually takes advantage of a phenomenon discovered over 150 years ago by British inventor Henry Fox Talbot (1836). Talbot found that when he allowed light to pass through a series of parallel slits in a screen (known as a diffraction grating or gradient), the light rays passing through the screen produced an intricate (and beautiful) interference pattern of regularly-spaced ‘peaks and troughs’ (light and dark lines/shapes). He found that this pattern repeats at periodic intervals. This light-interference pattern became known as the “Talbot carpet” or Talbot effect.

Subsequent experiments (McCall, 2010) with this phenomenon revealed a temporal version of the Talbot carpet; the effect can be manipulated in time to generate periodic events with zero light intensity — ‘time pockets’ — by pulling light waves apart and then putting them back together again (i.e., compressing the separated frequencies).

The New Temporal Cloaking Method

Expanding on these two key phenomena, Luken’s research team created their Talbot carpet using laser light. In this approach, the laser beam is passed through a phase modulator, which works as a wave guide. They then applied an oscillating electrical voltage to the guide. As they varied the voltage, the speed of the laser light was altered as well — splitting up the light into its constituent frequencies and pushing them ‘out of phase’ with each other. But these distinct frequencies recombined “destructively”, meaning that they cancelled out certain frequencies, generating ‘time holes’ (note: this step would correspond to Talbot’s discovery of light wave interference patterns as light passed through the slitted grating)

light waves evolving in time

Light waves, shown evolving in time in this simulation, create a cloaking effect at the middle where the light intensity goes to zero. (image credit: Nature)

However, these temporal holes have a very short lifespan (lasting less than a trillionth of a second). And so, Lukens and his team repeated the process so as to compress the total energy of the system and consequently lengthening the duration of the time holes (to 36 trillionths of a second, or 36 picoseconds).

The research team subsequently found that a significant volume of data can be cloaked by these ‘holes in time.’

Next, to test the method’s ability at cloaking actual data, the team inserted a new (encoded) data stream into the fiber during (in phase with) these time holes, or windows, and applied an additional two more rounds of phase modulation (to “undo” the phase changes from the first two rounds). This allowed the energy (laser light signal) to decompress and then recombine the separated frequencies back into one light signal.

Finally, the team confirmed that a downstream user (the recipient) would see only the original (unperturbed) laser signal; no trace of the time/phase modulation could be discerned. thus the method successfully cloaked the data — at a remarkable rate of 12.7 gigabits per second.

Watch this cool video demonstrating the cloaking principle (link opens new window – article continues below):

Refinements and Future Developments

The achievement is a fascinating ‘proof of principle’ that marks a rather unique advance for ‘cloaking technology’ which typically seeks to create ‘meta-materials’ and systems that manipulate or modify light waves to produce a zero refraction index. This in turn, creates the effect of light continuing in a straight line, as though there were nothing solid in between to cause light waves to deflect, or bounce off, in different directions (in general, this allows us to ‘see’ an object in our path). This particular advance, insofar as it involves temporal cloaking, and an immaterial “object” (data), does not require any such meta-materials.

Ironically, the new laser/optical method may just work a little too well at losing data in a time hole. “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,” says Lukens {source: see link below}

Nevertheless, Martin McCall (who originally proposed the temporal cloaking theory) is duly impressed and feels that future modifications will allow true, secure message transmission and other practical applications. The method can certainly provide a way to better shield information from noise corruption — a perennial problem in all communication systems.

The research was published under the title ‘A temporal cloak at telecommunication data rate in the journal Nature on June 5, 2013.

Some source material for this post came from the SciAm article: ‘Temporal Cloak Erases Data from History’ by Zeeya Merali (and Nature magazine)

 

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About the Author

Michael Ricciardi is a well-published writer of science/nature/technology articles as well as essays, poetry and short fiction. Michael has interviewed dozen of scientists from many scientific fields, including Brain Greene, Paul Steinhardt, Arthur Shapiro, and Nobel Laureate Ilya Progogine (deceased). Michael was trained as a naturalist and taught natural science on Cape Cod, Mass. from 1986-1991. His first arts grant was for production of the environmental (video) documentary 'The Jones River - A Natural History', 1987-88 (Kingston, Mass.). Michael is an award winning, internationally screened video artist. Two of his more recent short videos; 'A Time of Water Bountiful' and 'My Name is HAM' (an "imagined memoir" about the first chimp in space), and several other short videos, can be viewed on his website (http://www.chaosmosis.net). He is also the author of the ebook 'Zombies, E.T's, and The Super Entity - A Selection of Most Stimulating Articles' and for Kindle: Artful Survival ~ Creative Options for Chaotic Times



  • FactsAreFun

    I am having difficulty to see why this device would be a cloak. A cloak is something that hides a physical object be deflecting light around it, i.e. the light rays are moved perpendicular to their original direction. A temporal cloak does not have any perpendicular directions to hide things “behind”. It can merely reshuffle photons in time… the photons are still there, for everyone to detect. One can not make “nothing” out of something (if for no other reason than energy conservation). One may be able to make a pseudo-random signal out of the original signal, at best… but that’s not a cloaking but an encryption device.

  • FactsAreFun

    I am having difficulty to see why this device would be a cloak. A cloak is something that hides a physical object be deflecting light around it, i.e. the light rays are moved perpendicular to their original direction. A temporal cloak does not have any perpendicular directions to hide things “behind”. It can merely reshuffle photons in time… the photons are still there, for everyone to detect. One can not make “nothing” out of something (if for no other reason than energy conservation). One may be able to make a pseudo-random signal out of the original signal, at best… but that’s not a cloaking but an encryption device.

    • http://www.chaosmosis.net Michael Ricciardi

      Hi FAF

      thanks for your cogent comment. The method ‘cloaks’ (laser-transmitted) data by hiding it (in this case permanently!) in the cancelled phases (frequencies); this does not seem to be a ‘pseudo-random signal’ generation technique, but may be superficially similar.

      Also: your description seems to say that the method is polarizing (displacing perpendicularly) the original light wave signal (or some of it – the data part of it)…I am not sure if this was in fact done. Are there other ways to shift/alter light waves to obscure information other than polarizing some of the outgoing light?

      But, while I agree that the photons are still there (but “phase-shifted in time”), I do not think that “anyone can see them”…unless they knew exactly what phase-shifted modulation (temporal) pattern was used to hide the data (create the “time holes”) in the first place…similar to having an encryption key, etc.

      I think that reading the Nature paper will be more revealing on these issues.

      • http://www.chaosmosis.net Michael Ricciardi

        Note to my readers: the link in the research paper title has been fixed and should now point to he Nature.com paper (not the summary article about the paper).

        thanks, MR

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