It’s one thing to talk about an invisibility cloak that makes a person invisible, it’s another entirely when you talk about making an event invisible. That is exactly what Cornell scientists have done. Of course, they haven’t caused anything major to disappear like a top secret meeting, but they have shown that the possibility is there.
Cornell University scientists announced their finding in the January 5 edition of Nature. Alexander Gaeta, professor of applied and engineering physics, and colleagues performed their scientific feat using light beams through an optical fiber using a technique called four wave mixing. They call it a “time lens”.
They use a technique called four-wave mixing, in which two beams of light, a "signal" and a "pump," are sent together through an optical fiber. The two beams interact and change the wavelength of the signal. To begin creating a time gap, the researchers first bump the wavelength of the signal up, then by flipping the wavelength of the pump beam, bump it down.
Then the beam is sent through a long optical fiber where the two different parts of the beam pass each other creating a gap through which a flash of light is sent. More optical fiber reverses the process yet again the gap is closed. Another four wave mixer brings both parts of the light wave back into one with no sign of a gap.
The total time of the gap was 15 picoseconds, infinitesimal. They hope to get it up to 10 nanoseconds. OK forget about hiding a top secret meeting between politicians unless they’re gnats. Still there may be applications that would aid in the creation of computer chips that use light instead of wires.
The researchers got the idea from a proposal made by Martin McCall, a physics professor from Imperial College. He proposed the creation of a “space-time cloak or ‘history editor’”. Unfortunately, it required a material that doesn’t exist yet. It may in the future but not now.
So even as we get closer to creating a real invisibility cloak like the one Harry Potter has, we are also closer to creating a technology to creating a time cloak as well that may eventually cloak our actions.
A video illustration of the process can be found here.
Illustrations from Cornell University.