If we can use Einstein's theory of General Relativity to predict the physics surrounding certain objects we can not observe (internal structure of black holes for example) then we should be able to use theories of quantum mechanics to predict items we cannot see as well (such as parallel universes). I don't think that's true. In a practical sense, classical computers are still faster than quantum computers. In a theoretical sense, it hasn't been proven impossible for a classical computer to factor a number in polynomial time. The theory itself was incomplete because there is no mathematical way of calculating an observation, and without math to support it, a theory is merely a postulation. Scientists could not use observations as part of this theory, there was no way to accurately test an observation without mathematics behind it, thus rendering this theory incomplete. This paper is about Everett's theory that Schrodinger's equation applies at all times, therefore the wavefunction never collapses. The author takes Everett's theory and discusses the implications associated with the non-collapse of the wavefunction (i.e. parallel worlds). This paper is important because it discusses the probability of multiple universes, a theory that (so far) is beyond our limits of observation. The wave function is the mathematical formula we use to describe quantum objects. It is a wavering quantity that mathematically describes the wave characteristics of a particle. The value of the wave function of a particular particle at a given point of space/time is related to the probability of the particles being there at that time. Here is more information on wave functions https://www.youtube.com/watch?v=aowYf44gDRY Funny Everett’s thesis discussed the possibility that Schrodinger’s cat is both dead and alive, because the universe splits into two. In one universe, the cat is dead; in another, the cat is alive. Everett postulated that at each quantum juncture the universe splits in half, in an incessant sequence of splitting universes. Here is an example of Everett’s theory https://www.youtube.com/watch?v=KNwKPfOKipk Decoherence was Zeh's theory involving Schrodinger's cat. Zeh noticed that in the real world you could not separate the cat from the environment (air molecules, the box, cosmic rays passing through the experiment). Zeh claimed that these interactions, no matter how small, can radically affect the wave function. If the wave function is disturbed in the slightest way, then the wave function will suddenly split into two distinct wave functions of the dead cat or the live cat (which no longer interact). Zeh showed that a collision with a single air molecule was enough to collapse the wavefunction, forcing the permanent separation of the dead cat and the live cat, which no longer interact, In other words, before you even open the box, the cat has been in contact with the air molecules and hence is already dead or alive. Here is a video going more in depth about wave functions and decoherance https://www.youtube.com/watch?v=Zbe6ov22Nok This example is supposed to prove that nothing is truly "random" when it comes to probability, even if it appears so. The underlying physics proves the card falling is not random, 16 parallel worlds would exist in which this card has every possible outcome A quantum computer can solve problems that no classical computer would be able to solve within a reasonable amount of time. They would be able to decrypt the majority of the cryptographic systems in use today. Currently, Google and NASA are working on building a quantum computer, here is a video explaining more about quantum computers as a whole, and google and nasa's involvement. http://mashable.com/2013/10/13/google-quantum-computing-video/#KW2dQZTqnsq3 If you would like to learn more about parallel worlds and the science behind it, here is a short article/video http://www.dailymail.co.uk/sciencetech/article-2816039/Parallel-universes-exist-Multiple-versions-living-alternate-worlds-interact-theory-claims.html Schrodinger's cat - Imagine a cat enclosed in a box with a radioactive source. If a single atom of the radioactive source decays, a mechanism would trip a hammer, which would in turn, break the vial containing the radioactive source, and kill the cat. Until the source emits radiation, the cat would be considered (according to quantum mechanics) to be simultaneously both dead and alive, until the box is open, and the cat is observed. When the box is open, the “wavelength” collapses, and the cat can either be one of these two things: dead OR alive. Here is a brief video demonstrating Schrodinger’s cat and the implications behind observation https://www.youtube.com/watch?v=IOYyCHGWJq4 Everett's theory claims that decoherence explains why we don't perceive parallel universes. He claimed that perhaps the cat is dead and alive at the same time, but in different universes. The cat is both dead and alive because the universe has split into two. In one universe, the cat is dead, and in another universe, the cat is alive. If this interpretation is correct, then at this very moment, your body coexists with wave functions of dinosaurs, wave functions where the Germans won world war one, where aliens roam, where you were never born, etc. The catch is we can no longer interact with these wave functions, because they have decohered from us (the waves are no longer in phase with one another). This means the slightest contamination with the environment will prevent the various wave functions from interacting with one another, thus we are unable to perceive these parallel universes. Schrodinger’s equation is the basic equation for describing quantum behavior, and is constantly used in quantum mechanics. Also known as the Schrodinger wave equation, it is a partial differential equation that describes how the wavefunctions of a physical system change over time. In the past, observation of Schrodinger’s cat was said to “collapse” the wavefunction, thus leaving only one outcome (a dead or alive cat), however, Everett’s theory postulates that the wavelength never truly collapses, instead, the wavelength transforms into a parallel universe. In this case, if we were to open Schrodinger's box and find a dead cat, a parallel universe would be created where we open the box and find an alive cat. The wavefunction never collapses in Everett's view, they just continue to evolve, forever splitting into other wave functions in a never-ending tree, with each branch representing an entire universe. However, in our universe, we perceive the wavefunction as "collapsing" because decoherence only gives us one outcome. If in this universe the outcome is "a", we perceive the wavefunction as collapsing to "a", however, there is another universe where the wavefunction collapses to "b" and the people living in that universe perceive the wavefunction collapsing to "b". Thus, decoherence appears as if it produces an effect like a collapse separately in each parallel universe, however, on a large scale, the wavefunction never collapses. Everett's theory claimed that regardless of the size of the system, scientists will not observe a wavefunction collapsing, however, this theory will be disproven by future lab experiments. Decoherence is due to constant interactions with the environment, which are impossible to avoid. This explains that what we think of as an observation doesn’t require a human; simply interacting with the environment counts. This explains why bringing large objects into superpositions of two states is extremely difficult and the superposition fades rapidly. The heaviest object so fat that has been brought into a superposition of locations is a carbon-60 molecule. More ambitious scientists have proposed to do this experiment to viruses or even heavier creatures, such as bacteria. Thus, the paradox that Schrodinger’s cat once raised, (the transfer of a quantum superposition, the decaying atom, to a large object, the cat) has been resolved. Scientists now understand that while small things (atoms, quarks, ect) can exist in superpositions for extended amounts of time, a large object will settle extremely quickly in one particular state. That is why we never see cats that are both dead and alive.