For anybody reading this and having visions of teleporting to spaceships, this is not that kind of teleportation. Imagine two indistinguishable envelopes. Put

For anybody reading this and having visions of teleporting to spaceships, this is not that kind of teleportation. Imagine two indistinguishable envelopes. Put a red piece of paper in one of them and a green piece of paper in the other. Shuffle them so you don't know which is which. Have a friend take one of the envelopes a hundred kilometers away. Then open the envelope you still have with you. It contains the green piece of paper. WHOA INSTANT TELEPORTATION OF INFORMATION! You know that the other envelope has the red paper instantly, even though it is a hundred kilometers away! Information transfer faster than the speed of light. Amazing. Now, instead of using envelopes, imagine Alice generates a pair of entangled photons. Alice send one half to Bob and measures the other half. Since the photons are entangled, Alice knows what Bob must be measuring, just like with the envelopes. So what makes quantum teleportation special? What can we do with quantum teleportation that we cannot do with envelope teleportation? One interesting thing about the quantum world is that we cannot measure something without disturbing it. You can use that property to make an ultra-secure cryptographic system. Alice generates an entangled photon pair so that the photons are either 'pointing left' or 'pointing right' or 'pointing up' or 'pointing down'. Now, there is no way to measure directly what direction the photon is pointing in. You can choose among two tests. Test A gives you the correct answer if the photon is pointing left or right, but gives you a random result if it's pointing up or down. Test B gives you the correct result if it's pointing up or down but a random result if it's pointing right or left. Doing Test A or Test B completely disturbs the photon, giving it a random state. If Alice chooses a direction to measure randomly, and Bob chooses a direction to measure randomly, Bob's measurements will agree with Alice 75% of the time. Half the time, they'll choose the same method and their measures will agree, and half the time they will choose a different method and both get a random result, but through pure chance, they will still agree half the time. If Eve tries to do a 'Man in the middle' attack, intercepting Alice's photons and copying the result to send to Bob, Eve will send with only 75% accuracy and Bob's measurements will be only 62.5% accurate. Thus, Eve can be detected. Watch this video for more details: http://www.youtube.com/watch?v=UVzRbU6y7Ks http://www.youtube.com/watch?v=UVzRbU6y7Ks This result in the link is interesting because the researchers have been able to transport an 'entangled' photon over more than 100 kilometers, maintaining its state. It is quite hard to do since entangled photons are fragile. However, the photons are not being teleported, just transmitted, and sticking to the speed limit like good space citizens. It is not that Alice can make a change to her half of the entangled pair and have that be reflected in Bob's, it's just that Alice can MEASURE her half and know what Bob must be measuring.