Dec 29th 1959, Physicist Richard Feynman gave wonderful lecture entitled “There is plenty of room at the bottom” at an American Physical Society meeting at Caltech, where he presented a audacious and enduring vision of a technological advancements leading toward the atomic scale and toward the ultimate boundaries set by laws of physics. The world has traveled far toward what Feynman saw, and has far still to go. The way things are in the atomic world is totally different to large scale objects like bike and engines. We can’t rely on experience and common sense to guide us on how things are going to work at this level. And that can make some of the effects of quantum physics seem mystical and one of the strangest features is quantum entanglement.
Quantum entanglement, a bizarre feature of quantum physics, is a phenomenon where there is possibility of linking two quantum particles like photons, gravitons or atoms in a special way such that they act effectively two parts of the same entity. We can then separate them to the extent that we like and change in one is instantly reflected in the other. The link of entanglement works instantaneously at any distance. So it would be spooky action if it could be used to send a signal. Entanglement can be measured, transformed, and purified. A pair of quantum systems in an entangled state can be used as a quantum information channel to perform computational and cryptographic tasks.
According to quantum mechanics, we can have range of possibilities each having certain probabilities and state remain undefined until it is measured. Only after observation, we can acquire defined state and state of other possibilities is destroyed. Entanglement link is also based on probabilities. For spin entangled atoms, we can’t realize the state of atom accurately until it is measured as they have range of probabilities on the values of their properties. Suppose x and y are entangled pair and they are separated to the extent we wish. If one of the atom x is measured spin up then without measuring we can predict that another atom y is at spin down state instantly. After measurement, wave function, that describes the complex probability amplitudes of the two particles together, of those entangled pair is collapsed, no matter how far they are. We can generate such pair of entangled spin +1 and -1 by making collision of pair of spin 0 atoms and these will increase their kinetic energy to compensate for their loss of spin energy. After each of these collisions, the two fast moving entangled atoms will then head straight out of the atom trap in opposite directions.
Scientists in China have already succeeded in teleporting information between photons over free space distance of 10 miles, much further than the few hundred metres previously achieved. In most of the experiments related to teleportation, photon has been used. Here, two photons are used which are entangled in such way that if one’s quantum state is changed, the state of other also changes instantaneously. In latest experiments in China, pair of photons were entangled in the spatial modes of photon 1 & polarization modes of photon 2 and two types of telescopes were designed in which one serves as optical transmitting antenna and other as optical receiving antenna.
It has been predicted that minimum speed for entanglement is 10000 times the speed of light. However, according to Einstein’s theory of relativity, anything traveling faster than light would be going back in time. Einstein said there is an inverse proportion between speed and light, and that if one were to reach the speed of light time would stop. Therefore if you exceed the speed of light you would be travelling back in time. Of course there is always the possibility that Einstein was wrong about that. If he is true then information can be sent back to the past. But what will be consequences? If that is possible there must be cause and effect and consequences are horrible. That’s why quantum physics is full of absurdness.
Although these entangled pairs are able to communicate successfully, we can’t state precisely what actually has been transmitted. It has always been challenging tasks to develop a precise detector. To receive the information and to interpret it are different processes. Chinese talks are not exact information for us until we can interpret. It means though information was transferred, if we can’t interpret it then that is no more information for us.
There’s a fundamental problem associated with quantum teleportation. Because looking at a quantum particle changes it. We can’t scan a particle, see what it looks like and make an exact copy. So it might seem that teleportation is impossible. Entanglement let us get around this restriction.We can interact the particle with one half of an entangled pair, and then putting the other half of the pair through a special process, a bit like a logic gate in a computer, it’s possible to make an identical particle at a remote location. We can only do this because the entanglement transfers the quantum information without us ever knowing what it was. In the process, the original particle loses its properties. That’s means it follow cut and paste rule rather than copy and paste.
Does it possible to teleport human body in future?
Quantum entanglement is an experimentally verified fact. Human body comprises of billions and billions of such quantum particles. There has got to be a bunch of entangled particles somewhere in the universe. Luck, intution, telepathy, sympathy, empathy, love, hate, ego are a result of quantum teleportation into our minds. What we see in our dreams is also an effect of quantum teleportation from a distant particle. So if quantum teleportation can be precisely realised in future, it is possible to think about the concept of time machine. Human beings will not only able to be teleported but also able to travel in time machine. But it seems totally filled with absurdness.
- Zeilinger, A.; IEEE paper, “Quantum entanglement and information” Quantum Electronics and Laser Science Conference, 2000. (QELS 2000). Technical Digest Publication Year: 2000
- Weinfurter, H.; Bouwmeester, D.; Daniell, M.; Jennewein, T.; Jian-Wei Pan; Simon, C.; Weihs, G.; Zeilinger, A.; “Quantum communication and entanglement“ Circuits and Systems, 2000. Proceedings. ISCAS 2000 Geneva. The 2000 IEEE International Symposium on Volume: 2 Digital Object, Publication Year: 2000 , Page(s): 236 – 239 vol.2
- Prakash, H.; IEEE paper, “ Quantum Teleportation”Emerging Trends in Electronic and Photonic Devices & Systems, 2009. ELECTRO ’09. International Conference on Publication Year: 2009 , Page(s): 18 – 23