Why 'event cloaks' could be the key to the ultimate bank heist

July 1, 2011

In this month's 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 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".

Explore further: 'Space-time cloak' to conceal events revealed in new study

More information: Physics World: www.physicsworld.com/

Also in this month's special issue on invisibility.

  • Invisibility is now a reality, but scientists are not satisfied and are still searching for the holy grail – a cloak of invisibility that can hide macroscale objects from view at any angle, using unpolarized visible light. Wenshan Cai and Vladimir Shalaev map out the road ahead on this mission.
  • The quest to achieve true invisibility has inspired ambitious goals beyond merely cloaking visible light. Ulf Leonhardt takes a light-hearted look at the top five possible spin-offs from invisibility science.
  • Tales of invisible people and magical invisibility-bestowing objects have thrilled us for millennia. Sidney Perkowitz reveals how these myths and fantasies are now becoming a reality.

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4 / 5 (1) Jul 01, 2011
I imagine that a sufficiently perceptive observer would notice a 'dimming' as they view the slowed light, and a bright 'blip' as the 'compressed' light zips by.
But I'd be more confused if a security guard doesn't question why the masked men are putting an 'art installation' directly in front of the safe. ;-)
5 / 5 (1) Jul 01, 2011
The slowing the light down part I can imagine. However, the speeding the light up, as in making it go faster than normal, as in faster than the speed of light, needs a touch more explanation, IMO.
1 / 5 (1) Jul 01, 2011
The slowing the light down part I can imagine. However, the speeding the light up, as in making it go faster than normal, as in faster than the speed of light, needs a touch more explanation, IMO.

The speed of light in a medium is defined as c/n where n is the index of refraction of the medium. If this also holds true for metamaterials with n less than 1, then that would imply a faster speed of light. I don't know enough about the subject to know if this actually happens.
0.8 / 5 (50) Jul 01, 2011
Wouldn't accelerating light past its speed in a given medium produce Cherenkov radiation? Very pretty but not subtle.
5 / 5 (1) Jul 01, 2011
Cherenkov radiation is only produced by charged particles, not photons. The statement about photons moving slower than the speed of light in the vacuum is correct for propagation thru most materials. However, the index of refraction for air at STP is 1.000277 so the length of time required for the slow-down and subsequent speed-up might be very large if one wants to obtain a macroscopic amount of event cloaking.
not rated yet Jul 01, 2011
@Mayday, I've interpreted 'slowing' and 'speeding' up of light in terms of 'stretching' and 'compressing' the time between photons. Possibly wrong, but it allows me to work with the concept while avoiding the smell of burnt toast.

@sstritt, I did a little reading, and I don't think it's possible to have an absolute index of refraction less than one (|n|<1). Metamaterials can have a negative index of refraction, but never with a magnitude less than 1.

@FrankHerbert,PsiStar; I wasn't aware of Cherenkov radiation, now I am; THANKS! (Also thanks to Wikipedia for explaining it to me.)
1.3 / 5 (3) Jul 01, 2011
Maybe this technology already exist, and that is where all the legends came from. Its just not out in the public domain yet. For instance the U.S. Space Command has bases on the moon and Mars, but we use NASA as a way to filter the technology to the public domain.
4 / 5 (1) Jul 01, 2011
I wonder what use 'event cloaking' could be in testing where you might want to 'isolate' the test for a period.

As to the mention at the end of invisibility stuff, I'd love to see one developed for the dangerous radiations. It might just be lighter and more effective than our current shielding.

With regards to Cherenkov Radiation. That's some pretty stuff, to bad it's usually found in places that tend to kill humans. Guess we just have to enjoy the pictures.
3 / 5 (6) Jul 01, 2011
Whatever happened to good old ether pumped through the ventilation system?
5 / 5 (1) Jul 03, 2011
As to the mention at the end of invisibility stuff, I'd love to see one developed for the dangerous radiations. It might just be lighter and more effective than our current shielding.

It's hard enough to make this work at visible wavelengths, and now you want it for X-rays and Gamma rays? Sigh... Some people are never satisfied. :)
1 / 5 (1) Jul 05, 2011
So you take a image/video of the area to be slowed/stopped, place a replay device in front of the security camera reply/display the scene.
As long as no expected event occurs, visible clock now static/slow, another security guard doing appointed rounds goes missing etc the illusion holds
The darkness equates to the transition from real-time to recorded image.

Hasn't this premise for this analogy been in countless movies & TV shows. ? :(
5 / 5 (1) Jul 17, 2011
If you could afford to create this, why would you need to rob a bank?
not rated yet Jul 18, 2011
Maybe 'you' didn't use your own money to build it, but was funded by someone else? I'd steal the tech, then use it to make my fortune.

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