Scientists Punch a Hole in the Fabric of Time with a "Time Cloak"
2011-07-18 0:00

From: technologyreview.com



Physicists have created a "hole in time" using the temporal equivalent of an invisibility cloak.

Invisibility cloaks are the result of physicists' newfound ability to distort electromagnetic fields in extreme ways. The idea is steer light around a volume of space so that anything inside this region is essentially invisible.
The effect has generated huge interest. The first invisibility cloaks worked only at microwave frequencies but in only a few years, physicists have found ways to create cloaks that work for visible light, for sound and for ocean waves. They've even designed illusion cloaks that can make one object look like another.

Today, Moti Fridman and buddies, at Cornell University in Ithaca, go a step further. These guys have designed and built a cloak that hides events in time.

Time cloaking is possible because of a kind of duality between space and time in electromagnetic theory. In particular, the diffraction of a beam of light in space is mathematically equivalent to the temporal propagation of light through a dispersive medium. In other words, diffraction and dispersion are symmetric in spacetime.

That immediately leads to an interesting idea. Just as its easy to make a lens that focuses light in space using diffraction, so it is possible to use dispersion to make a lens that focuses in time.

Such a time-lens can be made using an electro-optic modulator, for example, and has a variety of familiar properties. "This time-lens can, for example, magnify or compress in time," say Fridman and co.

This magnifying and compressing in time is important.

The trick to building a temporal cloak is to place two time-lenses in series and then send a beam of light through them. The first compresses the light in time while the second decompresses it again.

But this leaves a gap. For short period, there is a kind of hole in time in which any event is unrecorded.

So to an observer, the light coming out of the second time-lens appears undistorted, as if no event has occurred.

In effect, the space between the two lenses is a kind of spatio-temporal cloak that deletes changes that occur in short periods of time.

The device has some limitations. The Cornell time cloak lasts only for 110 nanoseconds--that's not long. And Fridman and co say the best it can achieve will be 120 microseconds.

But it's early days yet. Given the rapid development of spatial cloaks, it'd be a brave man who'd bet on this being the last word.

Fridman and pals have clearly made themselves an interesting toy but they modestly refrain from speculating about the applications for their time cloak.

However, that's a task well suited to readers of the Physics arXiv Blog. If you have any suggestions, leave them here.

Ref: arxiv.org/abs/1107.2062: Demonstration Of Temporal Cloaking



Related Articles


Latest News from our Front Page

CDC official called Obama 'Marxist,' 'amateur' over border surge...
2015-07-08 0:28
Following the influx of illegal immigrant minors from Central America, an official at the federal agency charged with protecting public health describes Barack Obama as "the worst pres we have ever had," an “amateur" and "Marxist," according to internal emails obtained by Judicial Watch. JW got the records as part of an investigation into the Center for Disease Control’s (CDC) activation ...
Obama Administration Likely to Block New Redskins Stadium
2015-07-07 23:03
The Obama administration will likely block Washington, D.C., authorities from building a new stadium for the NFL’s Washington Redskins because of objections to the team’s name. The National Park Service (NPS) owns the land under the 54-year-old Robert F. Kennedy Memorial Stadium, a venue two miles east of the Capitol that hosted the Redskins from 1961 to 1996. Some city leaders ...
Safe spaces, white tears and getting kicked out of a women's group - by two men
2015-07-07 21:37
Lately I've been kicked out of a couple of groups I belong to, for daring to question received wisdom or refusing to go along with the rules of identity politics. For instance, I was thrown out my university women's group -- by two men! -- for questioning an article on Jezebel about "cultural appropriation." They explained that the group was supposed to ...
Ghost rider in the sky: Scientists use lasers to project movie onto clouds
2015-07-07 20:08
A green ghost rider appeared in the sky over the British city of Nottingham when scientists started testing a newly developed projecting device which allows the beaming of moving images directly onto clouds for the first time ever. The image of a galloping horse rider was projected onto the clouds from a distance of 50 meters by a special laser-based projection ...
China’s stock market is crashing, and the Chinese are trying to do the exact same thing America did in 1929
2015-07-07 19:36
‘While European attention is focused on Greece, China is having a serious market meltdown. After exploding earlier in the year because of deregulation, China’s benchmark Shanghai Composite has collapsed a crazy 29% since the highs of early June. China’s other stock markets have had similarly steep falls. Bloomberg notes that the crisis is closely mirroring the 1929 Wall Street crash, which led ...
More News »