In a special issue of Physics World, which examines the science
and applications of invisibility, Martin McCall and Paul Kinsler of
Imperial College London describe a new type of invisibility cloak that
does not just hide objects—but events.
Using
the ultimate bank heist as an example, McCall and Kinsler explain how a
thief could, in principle, use an “event cloak” to steal money from a
safe, without even the CCTV surveillance cameras being aware.
The
burglar would somehow need to split all the light approaching the safe
into two parts: “before” and “after”, with the “before” part sped up and
the “after” part slowed down.
This
would create a brief period of darkness during which the burglar could
enter the scene and steal the money, being careful to close the safe
door before they leave.
With
the safe-cracker gone, the process of speeding up and slowing down the
light would then be reversed, leading to an apparently untouched scene
once again.
Robbing
a bank is, of course, only an example to illustrate the principle of
what an event cloak could do. As McCall and Kinsler explain, a more
likely application of a full-size event cloak would be to control the
flow of signals in an optical routing system, where one may need to
process simultaneous uninterrupted signals at the same time.
For
these aspirations to become a reality, suitable materials need to be
developed that can manipulate the light to speed it up or slow it down.
The consensus seems to be that a set of parallel, artificially
structured “metamaterial” layers would be needed, each containing an
array of tiny metallic elements that can be controlled to dynamically
adjust the speed of light passing through.
If
a high-performance, macroscopic-size, fully functional space–time cloak
could be developed, one potential “party trick” could be a Star
Trek-type transporter, in which a person could appear to instantly
relocate from one point to another.
Although
no one has yet tried to build a space–time cloak in the lab, McCall and
Kinsler argue that “there is no obvious reason why such a cloak could
not be achieved quite soon, perhaps even within a few years”.
SOURCE: www.iop.org
