Laser Beam Teleported

Michael Wardle writes "ABC Australia reports that a team of scientists from the Australian National University have successfully teleported a laser beam. It seems that teleportation of solid bodies is still a way off, but at least we're a little closer to Slashdot's favorite super power." Another Australian newspaper has a more detailed story.

Comments

Replication or Recreation -- not an easy question

[serutan]

The blueprint analogy shows a lack of understanding of entanglement. There is no blueprint at the receiving end, and no measurement and communication of instructions to replicate the properties of the sending photon. What happens is a seemingly spontaneous change in the properties of the receiving photon.

Whether this is teleportation or replication is more of a philosophical question, or maybe a matter of semantics. Is an object (or a laser beam) equal to the sum of its properties? If you can make the sum total of an object's quantum properties disappear from one place and reappear in another place, have you merely copied the object or have you moved it?

I think you've moved it, but questions like these deserve more than offhanded answers.

Re:Faster than super fast!

[037]

Yeah, FTL communication is cool, and I would agree that it is vital if it were at all possible, and I mean at all. It's not. The truth is that this type of laser teleportation is pretty arcane stuff, and doesn't move faster than the speed of light.

The question is begged, "what is the point of making a a laser go the speed of light? Isn't that like making a german sheppard go the speed of dog?" and the answer is um, sort of. Because the laser is reconstructed at the other location sort of faster than the speed of light, in that half of it arrives instantly (FTL) and the other half arrives at the speed of light.

This doesn't make any sense, but that's cool, so we'll keep going. The important thing to note is that the two halves of the laser beam (not really half, in the terms of 1/2 intensity or anything like that, it's more about the polarization, but we'll gloss over that) are needed to transmit any information. That's any information at all, including if the laser is even turned on or not.

That means that half of the laser can arrive from Jupiter, and the other half is en route for however long it takes for light to get here from Jupiter and you pretty much have to wait around.

(Actually, you can do a whole bunch of nifty calculations while you're waiting, and this is usually a good idea, but I've already dreadfully confused myself so let's skip that part.)

Then your speed-of-light transmission arrives with the other half of the data and you can reconstruct the original. Which is fabulous, and actually quite exciting, but importantly not faster than the speed of light.

Information turns out to be limited just like everything else is by the universal speed limit of 3X10^8m/s. So, if you want to go past, say, Mars, you're going to have to be ready for some lag on your phone call home. It's sad, but it's true.