Erasing history? Temporal cloaks adjust light's throttle to hide an event in time

Oct 12, 2011

Researchers from Cornell University in Ithaca, N.Y., have demonstrated for the first time that it's possible to cloak a singular event in time, creating what has been described as a "history editor." In a feat of Einstein-inspired physics, Moti Fridman and his colleagues sent a beam of light traveling down an optical fiber and through a pair of so-called "time lenses." Between these two lenses, the researchers were able to briefly create a small bubble, or gap, in the flow of light. During that fleetingly brief moment, lasting only the tiniest fraction of a second, the gap functioned like a temporal hole, concealing the fact that a brief burst of light ever occurred.

The team will present their findings at the Optical Society's (OSA) Annual Meeting, Frontiers in Optics (FiO) 2011, taking place in San Jose, Calif. next week.

Their ingenious system, which is the first physical demonstration of a phenomenon originally described theoretically a year ago by Martin McCall and his colleagues at Imperial College London in the Journal of Optics, relies on the ability to use short intense pulses of to alter the speed of light as it travels through , in this case an . (In a vacuum, light maintains its predetermined speed limit of 180,000 miles per second.) As the beam passes through a split-time lens (a silicon device originally designed to speed up data transfer), it accelerates near the center and slows down along the edges, causing it to balloon out toward the edges, leaving a dead zone around which the curve. A similar lens a little farther along the path produces the exact but opposite velocity adjustments, resetting the speeds and reproducing the original shape and appearance of the .

To test the performance of their temporal cloak, the researchers created pulses of light directly between the two lenses. The pulses repeated like clockwork at a rate of 41 kilohertz. When the cloak was off, the researchers were able to detect a steady beat. By switching on the temporal cloak, which was synchronized with the light pulses, all signs that these events ever took place were erased from the data stream.

Unlike spatial optical cloaking, which typically requires the use of metamaterials (specially created materials engineered to have specific optical properties), the temporal cloak designed by the researchers relies more on the fundamental properties of light and how it behaves under highly constrained space and time conditions. The area affected by the temporal cloak is a mere 6 millimeters long and can last only 20 trillionths of a second. The length of the cloaked area and the length of time it is able to function are tightly constrained—primarily by the extreme velocity of light. Cloaking for a longer duration would create turbulence in the system, essentially pulling back the curtain and hinting that an event had occurred. Also, to achieve any measurable macroscopic effects, an experiment of planetary and even interplanetary scales would be necessary.

Explore further: Researchers seek broadband/multiband electromagnetic absorbers based on plasmonic and metamaterial structures

More information: FiO presentation FMI3, "Demonstration of Temporal Cloaking," by Moti Fridman et al. is at 4:45 p.m. on Monday, Oct. 17. http://www.frontiersinoptics.com/

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User comments : 14

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antonima
not rated yet Oct 12, 2011
In soviet russia history cloaks you!
richgibula
not rated yet Oct 12, 2011
I thought that happened in Kazakstan.
dub1
1 / 5 (1) Oct 12, 2011
The link wasn't very informative. I checked briefly before commenting. It seems they are confusing the measuring ability of their manipulated photons with what is going on inside. Or it's just another sensationalist headline. Erasing implies, well, erasing something that is already there.
Isaacsname
5 / 5 (1) Oct 12, 2011
They must not have been very successful, I could swear I read about this a few months ago.
astro_optics
1 / 5 (1) Oct 12, 2011
If we lived in the universe entirely made out of Photons...that might make sense!
Daleg
not rated yet Oct 13, 2011
Essentialy that is exactly what they did do. the Photons are known to have been emitted, but where not detected. That menas light that was there, disappeared inside the experiment. The time and distance constraints are the most interesting point, in that this is a short term effect over a tiny distance, which causes it's own downfall if pushed to a macroscopically useful level, meaning that event cloaking or erasure, is another weird quantum effect, that we would or probably should not per se be able to experience at our usual level of reality. This then begs the question as to why these odd results occurr in the first place. Something to do with our misperception of how reality really functions, at least on the microscopic level, and how it takes a whole lot of weirdness to produce our humdrum every day world in the first place.
dub1
1 / 5 (1) Oct 13, 2011
The fact that they could not detect, in their limited experiment, doesn't really say much. The source link says even less. I can sound-proof a room by using iffy microphones by these standards. I can also make the room invisible, just not retestably so.
driverdoug
1 / 5 (1) Oct 13, 2011
This is an excellent proof of why our ferrimagnetic minerals such as in the rapidly cooled lava beds near Battle Mountain, NV show up rarely, leading us to believe that the period of pole shift reversals occur infrequently over 1 ma. The moments of extreme vector forces on our core come from extrasolar or extraplanetismal bodies, such that the Sumerian text or Mayan Calendar periods of 3,600 to 5,125yrs make more sense. Infrequent extreme deviation with Kurtosis using a Bernoulli process instead of Cauchy-Lorentz which admits moments do not exist. This experiment in a perfect snapshot of a moment that does not exist, and why our written word only goes back a few thousand years, and not in millions. The dynamo change in our core via the rock record has been erased. We aren't fully realizing the Lorentz force upon our landmasses or seafloors. Tachoclines and Taylor Columns return to normal so quickly, that we miss the event entirely.
unknownorgin
3 / 5 (2) Oct 14, 2011
I thought the speed of light was 186,000 m.p.s. not 180,000 plus or minus according to conditions.
hush1
not rated yet Oct 15, 2011
Good catch.
Oh my. I'm getting bad vibes. If gravitational waves exist, then negative dispersion exists for this.

I need to find a physical meaning for this.
hush1
not rated yet Oct 15, 2011
Pirouette
1 / 5 (1) Oct 15, 2011
It may be possible that the main body of the photons were still in the tube, but may have broken down into a much smaller arrangement of subatomic particles, which would have appeared to disappear, if such a thing can happen with light.

""By switching on the temporal cloak, which was synchronized with the light pulses, all signs that these events ever took place were erased from the data stream.""
Perhaps the data stream needs a little tweaking.
antialias_physorg
not rated yet Oct 17, 2011
I thought the speed of light was 186,000 m.p.s. not 180,000 plus or minus according to conditions.

It is (plus) or minus according to the medium. Light moves slower in a medium (like an optical fiber or a silicon split-time lens) than it does in a vacuum. Maximum speed of light is defined in a vacuum and nothing can go faster that this (unless the OPERA neutrino experiments turn out to be true...then things have just gotten a whole lot more interesting - and weirder - than they already are)

A time-split lens can be used to open up a gap in a datastream that was coninuously sent from a source and seem to be continuously received at the target. Something could be pushed throug the gap and the receiver would never know. While these gaps are tiny they are large enough for potential applications in photonic computing (switching, beam crossing, ... )
rawa1
not rated yet Oct 17, 2011
IMO it's normal spatial cloak - the true temporal cloak should separate you from running of time outside. You should stop getting older when being surrounded with such temporal cloak, you should freeze in time.

One of drawbacks of spatial cloaks is, they separate you from surrounding space too and the temporal cloak would work in the same way.