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One piece closer to a working electronic quantum computer puzzle kit.

Many believe the next generation of supercomputers will be powered by quantum mechanics. Harnessing the strange properties of photons and electrons in special states is often the backbone for quantum computer research. Some of these seemingly exotic properties have already been demonstrated using photons, but until very recently, were not replicated in solid-state systems by electrons.

A group of European researchers, consisting of institutions from France, Spain and Germany, has published their work with quantum entanglement using electron (Cooper) pairs, quantum dots and carbon nanotubes. Quantum entanglement is a quantum state of matter where two particles, typically photons or electrons, form a matched pair based on their physical qualities such as up or down spin for electrons and polarization for photons. When a pair of these particles becomes entangled, quantum mechanics states that measuring one of the pair will instantly force the unmeasured into a corresponding state, regardless of the distance they have been separated by.

In photonics work, researchers used wave guides and polarization filters to form entangled photons, which can then be separated by a beam splitter and measured individually. But for electrons, the work is far more taxing. Measurements are more easily skewed by background noise and leakage from the components of the test device.

The solid-state device used to confirm electron quantum entanglement is fairly simple in design. A superconducting element is used to form Cooper pairs. The pairs then move down the element towards a carbon nanotube. Occasionally the pair is split by the nanotube and each electron moves towards a separate quantum dot. In this time, one electron’s spin can be measured, which infers the spin of its mate instantaneously. These pairs can either be spin-correlated or anti-spin-correlated (spinning in the same direction or opposite directions), but the measurement of one always reveals the properties of the other.

Quantum entanglement could be very useful in theory, especially for quantum computing in the areas of security and data transmission. Theoretically, data can be transferred over any distance instantly and without any risk of security breech, however, the entangled pair still has to be transferred through physical media at this time.



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By foolsgambit11 on 1/13/2010 1:33:21 PM , Rating: 2
You're forgetting that, in quantum physics, until measured, the particles are considered to exist in both states, and neither. What you've described seems to be local realism - i.e., that the state already existed, and then we just measured it. Unfortunately, experiments have all but disproved that this is the case. I can't say that I understand it all myself, but that's why I trust a competent authority to let me know the scientific consensus. Anyway, look up "Bell test experiments" on Wikipedia, and know that when they're talking about local hidden variable theories, they're talking about theories that try to preserve local realism, as you described it.

In other words, I'm pretty sure that tens of thousands of particle physicists haven't been engaging in one big thought experiment - "ooh, what if particles weren't definite until we looked, and before that, they were everything! and nothing!" - for the past 80 years without justification. There actually is experimental evidence that particles don't have a specific state until measured.


By GourdFreeMan on 1/13/2010 3:32:51 PM , Rating: 2
http://en.wikipedia.org/wiki/Superdeterminism

False premises lead to false conclusions.

You would be surprised how enduring erroneous beliefs are when they are essentially philosophical rather than matters of scientific practicality.


By foolsgambit11 on 1/14/2010 12:05:46 AM , Rating: 2
Yes, that is always a possibility, I suppose. And it can't be ruled out any more than an omnipresent, omnipotent, omniscient god can be. The point, though, is that from a scientific standpoint, the theory that has the most predictive power given our current level of knowledge is the one I described above. To conflate a predictive theory with a philosophical argument simply muddies the issue.

I would love for quantum mechanics to suddenly become clear and somewhat-more-sensible, like our understanding of electromagnetism did, progressing from philosophical constructs about the aether, with all of its relatively arbitrary properties, to the elegant (if slightly mind-bending) theory of special relativity. But the theoretical construct (the 'why', so to speak) isn't really the point. The math is; the facts are. Special relativity doesn't explain the 'why' either. It does explain and predict the who, what, when, and where, though. That is the point of science. Scientific theories must have predictive power. Quantum mechanics has it, while superdeterminism is useless - it's just throwing our hands up in the air.


By SlyNine on 1/14/2010 5:23:32 AM , Rating: 2
We are not talking about beliefs, we are talking about theories that can be tested and potentially disproved.

So far the tests show the theories to be accurate, so if you are attacking the theory then you're the one that needs to consider using valid premises and offering a conclusion.


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