Quantum+Tunneling

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=Introduction:=

Quantum tunneling is an emission of alpha rays in radioactive decay. The alpha particles are strongly bound to the nucleus, but at the same time, the alpha particles still have a finite probability of escaping the nucleus. A wave determines the probability of where a particle may be found. When a wave encounters an energy barrier most of the wave will be reflected back, however a small portion of the wave will go into the barrier. If the barrier is small enough, the wave that went into the barrier will go through it. Even though the particle doesn't have enough energy to get over the barrier, there is still a small probability that it can go through it, or tunnel. media type="youtube" key="6LKjJT7gh9s" height="344" width="425" align="center"



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Explanation of Quantum Tunneling:
An experiment to explain this phenomena can be shown through a rubber ball and a wall. You don't have enough energy to throw the ball through the wall, so you always expect it to bounce back to you. Using the Quantum tunneling theory you could say that there is a small probability that the ball could go right through the wall (without damaging the wall) and continue its path to the other side of the wall continuing to bounce. When you have something as large as a rubber ball, there is a small probability that you could throw the ball for billions of years and never see it go through the wall. But if you use something small like an electron it is possible. However, when a particle encounters a //drop // in energy there is a small probability that the particle will be reflected. If you rolled a marble off a flat, level table, there is a small chance that the marble would reach the edge and that it would bounce back instead of dropping to the floor. When you have something large, like a marble there is a very small probability that this will actually happen. But if you use photons which are massless particles of light, there is a higher probability that this will happen. Another example is if you roll a ball up a hill. If the ball does not have enough velocity it will not roll over the hill but, it will roll back down it. However, using the idea of quantum tunneling these objects do not behave like that. These objects can go through an energy state using the wavelike behavior that quantum physics explains. If the particle is small enough (not a big ball) then it can tunnel through to the other side of the hill.

Uses of Quantum Tunneling:
Life today would not be the same without the idea of Quantum Tunneling. For example, the idea of Quantum Tunneling is used to make computer chips. If we did not use computer chips, one computer could take up a whole room and it would be very hard to manage. Quantum tunneling has also possibly helped to make our world and earth what it is today. It is essential for the nucleosynthesis of stars. Quantum tunneling also helped in the early evolution of our universe. Scientists have noted that when a collection of superconducting electrons put in an ultrathin superconducting wire were able to go through from a state of higher electrical current to a state of lower current. This provides more evidence that macroscopic quantum tunneling can occur. These particles are very small which helps them be able to go through to a lower current. Physics professors Alexey Bezryadin and Paul Goldbart led a team, with a graduate student Mitrabhanu Sahu performing the bulk of the measurements on the wires and what was happening. “Observing switching events in superconducting nanowires at high-bias currents provides strong evidence for quantum phase slips,” Bezryadin said. “Our experiments provide further evidence that the laws of quantum mechanics continue to govern large systems, composed of many thousands of electrons, acting as a single entity.”

There is a new experiment in the DESY particle accelerator in Germany called the standard model of elementary particles. There are Experiments being done by shining a light through a wall which could reveal particles that are not predicted by the standard model. For example, the particle that DESY is looking for is called the WISP (weakly interacting sub-eV particle), which could be a major component of dark matter. The standard model does not account for dark matter, which is why any discovery in this area would be amazing for particle physicists.  The DESY experiment is a high-tech wall. On one side of the wall is a laser, and on the other is a detector. The trouble is that photons transform into WISPs very rarely. So you need a huge number of photons to see the effect. The DESY team has a powerful laser producing some 10^19 photons per second, but that is not enough. So the researchers have built themselves a couple of mirrors to reflect the photons back and forth, so that each photon approaches the wall around 200 times. Now the researchers need to wait, and watch, and in the future results will be announced.