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This blog is all about science and technology (with occasional math thrown in for fun). The goal of this blog is to try and pass on the sense of excitement and wonder I feel when I read about these topics. I hope you enjoy the posts.

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Quantum Superposition on a Classical Scale

Posted December 30, 2015 7:52 AM by Bayes

Bose Einstein Condensates as tools

Bose-Einstein condensates are states of matter in which separate atoms (or subatomic particles), cooled to near absolute zero, coalesce into an object that can be described by a single wave function. First predicted in 1924-25 by Satyendra Nath Bose and Albert Einstein, it wasn't produced in a lab until 1995 when Eric Cornell and Carl Wieman at the University of Colorado at Boulder cooled a gas of rubidium atoms to 170 nanokelvin.

Bose-Einstein condensates are useful tools for studying quantum mechanical properties. Because their momentum is so low (due to their low temperature), they exhibit quantum behavior at larger scales (due to the uncertainty relation between momentum and position). Momentum is mass times velocity (temperature is a measure of internal motion) so the larger the number of atoms involved in the condensate, the more mass involved, which means the more precisely the momentum is known for a given temperature and thus the more macroscopic the quantum mechanical effects that can be observed (again due to the uncertainty relation).

Recently scientists have demonstrated one of the more interesting properties of quantum mechanics, the concept of superposition, but on the meter scale. Here is an article describing the experiment and its results.

New quantum record as ball of atoms ends up in two spots at once

Try to imagine a tiny ball sitting on one fingertip yet also on your shoulder at the same instant. Are you struggling? Most of us can't conceive of an object being in two places at once - yet physicists have just demonstrated the effect over a distance of half a metre, smashing previous records. It's an example of superposition, the idea that an object can exist in two quantum states at the same time. This persists until it is observed, causing a property called its wave function to collapse into one state or the other. The same principle allows Schrödinger's cat to be both dead and alive inside a box until you open the lid.

We often think of quantum mechanics as applying only to subatomic particles, but there is nothing in the theory that limits its range. That's why experiments try to probe the transition between the quantum and everyday realms. "We're all wondering whether there is some regime where superpositions turn into classical states of matter," says Mark Kasevich of Stanford University in California. To find out, Kasevich and his colleagues created a Bose-Einstein condensate (BEC) - a cloud of 10,000 rubidium atoms, all in the same quantum state. They shot this cloud, just a few millimetres across, up a 10-metre-high chamber using lasers, which also gradually push the atoms into two separate states.

By the time the BEC reaches the top of the chamber, its wave function is a 50-50 mixture of those states, representing positions 54 centimetres apart. It stays in this superposition for about a second, then falls back down. At the bottom, the lasers turn the two states back into one, and this reveals that the atoms appear to arrive from two different heights, confirming that the BEC was indeed in a superposition at the top of the chamber.

Article Continues Here

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Re: Quantum Superposition on a Classical Scale

12/31/2015 10:54 AM

The brain is a quantum computer and this is why I can't make a decision!

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Re: Quantum Superposition on a Classical Scale

12/31/2015 12:19 PM

Just don't open the box to see if the brain is alive, you might encounter the 50% chance of finding it dead. Brains are just cats that have not yet emerged. Hence the expression: "He/she has cat sheite for brains".

On a more serious note, I think BEC's may play some major role in all forms of LENR, but in that case it is not the momentum that is constrained, just the fixed position of hydrogen atoms (and isotopes) within a metal or other crystalline lattice.

Perhaps this will lead to an energy breakthrough in the near future, since one company , Brillouin Energy, plans to go public once they pass through the 3 COP barrier, and at last count they had already succeeded in 2.6 COP. The COP is the ratio of heat output to heat (energy) input. Check 'em out!

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