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What is quantum mechanics?
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The world reduced
Additional Photography: Christoph Lackner (2), Universität Innsbruck
When researchers advance into the very smallest components of matter, different laws of physics apply to those of our everyday world. Very different laws For a long time, Newtonian physics was the be-all and end-all. In the 17th century, Isaac Newton formulated his laws of gravity and motion, thus establishing our understanding of the world. Using these laws, everything worked and could be explained clearly and logically, apart from comets, vampires and swarms of locusts, that is. At the dawn of the 20th century, however, this perfect order, with its laws that were clear to us even if we didn’t understand the underlying mathematics, began to falter, because the laws of Newtonian physics applied to the world at large but weren’t much use when it came to the smallest dimensions. What Max Planck, Werner Heisenberg, Niels Bohr and others asserted in the early decades of the 20th century questioned everything that had until that point been considered certain, and completely new findings had to be accepted. Energy cannot be changed continually, but only in small amounts (quanta). Electrons suddenly no longer moved in circles around the atomic nucleus but followed a probability distribution. Things were one thing and something else at the same time, so light, depending on how the experiment was set up, could be a wave or a stream of particles and in actual fact was clearly both simultaneously. Particles such as photons (light particles) could become entwined with other particles and, to put it very simply, interact with them instantaneously (quicker than the speed of light), regardless of distance (even millions of kilometres). And by observing something, we change it. An elementary particle changes speed when we measure it (by casting light on it, for example). This last point gives rise to one of the cornerstones of quantum physics: it is impossible to calculate the speed and location of a particle at the same time. Quantum physics has seen indeterminacy and probability establishing a foothold in the world of science. Admittedly, this all affects man and his macrophysical day-to-day life very little. Apart from the fact that without quantum physics there wouldn’t be CD-players, transistors or computers here today. Strictly speaking, we wouldn’t be here either.
1 The heart of an Ion trap, where the electrically charged atoms are put in order and their quantum properties calculated 2 Quantum physics has a bit of a PR problem: without the required mathematical basis, it’s quite difficult to understand 3 A laser brings the Ions down to almost absolute zero, which might be a bit impractical when trying to build a quantum laptop
identical quantum properties. Ions in traps like these can now calculate that the factors of the number 15 are 3 and 5. “Exactly the answer we were expecting,” says Zoller, without missing a beat. So if we’re comparing the research to scaling Mount Everest, we’ve just about made it out of Vienna. “But just think how regular computers started in the 1930s with the most basic electric circuits,” adds Zoller. The Austrian scientist wants his quantum technology to have broad application. “Quantum information, quantum computers, quantum simulation in material research; it’s not just about a super-computer,” he says. “What we won’t have is desk-top quantum computers. We don’t need those.” He gives a nice example of how a quantum computer would be superior in material calculation. “Take a magnet whose magnetism is defined by, among other things, the intrinsic angular momentum of its electrons. If I want to analyse just 300 electrons in relation to this momentum, I have 2 to the power of 300 possibilities, which is approximately how many atoms there are in the universe that we can see. A quantum computer can calculate all those momentums at the same time. A normal computer would have to have 2 to the power of 300 storage cells, ie have the atoms of all the matter in the world.” And who would be left to operate it? To discover more about the Institute for Quantum Optics and Quantum Information in Innsbruck visit, www.iqoqi.at
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