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Researchers Control the Flip of Electron Spin
karvind writes "According to PhysOrg, physicists in Europe, California and at Ohio University now have found a way to manipulate the spin of an electron with a jolt of voltage from a battery. In this experiment voltage was applied to Indium Arsenide based quantum dot which flipped the spin of electron inside it and emitted a photon. The scientists were able to manipulate how long it would take for the electron to flip its spin and emit a photon - from one to 20 nanoseconds. This may have possible applications in optoelectronics and quantum cryptography. Results were published in the latest issue of Physics Review Letters"
Was I the only one who thought this read "Researchers Control the Flip of Election Spin"?
All universities new findings take 30 years before they are applied to the corporate world.
1.) show the slashdot how electron flips
2.) slashdot crowd say cool
3.) show more engineers
4.) show sponsors, marketers, businessmen
5.) repeat step 4 for 29 years
6.) profit!
*...voltage was applied to Indium Arsenide based quantum dot which flipped the spin of electron inside it and emitted a photon. The scientists were able to manipulate how long it would take for the electron to flip its spin and emit a photon - from one to 20 nanoseconds.*
When you put it that way, I don't know why it wasn't this simple the whole time!
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The title of the linked-to article in Physical Review Letters is:
"Voltage Control of the Spin Dynamics of an Exciton in a Semiconductor Quantum Dot"
(Emphasis by be)
Now an exciton is something quite different from an electron.
The Tao of math: The numbers you can count are not the real numbers.
"A dark exciton with total angular momentum L=2 ecomes a bright exciton with L=1."
Finally a practical application for decay dynamics following nongeminate excitation
I found myself reading this article quite mindful of the frequency of stories recently that suggest the US is headed down a dangerous path of neglect and ignorance. Not only in the arena of biological research (stem cell, et al) but in technological developments as well. This is not a matter of observation but rather official administrative policy http://science.slashdot.org/article.pl?sid=05/04/0 2/183230&tid=98&tid=103&tid=190&tid=215&tid=231&ti d=14 .
"The study was funded by EPSRC in the United Kingdom, Ohio University, Volkswagen, and the Alexander von Humboldt Foundations, with additional support by the Scottish Executive and the Royal Society of Edinburgh"
It seems to me that this is exactly one example of the type of technology the government should be promoting, for military benefit or not. What I am not sure of is wether the researches had the option to solicit US funding or if they chose rather to not bother?
I don't know, it struck me as a little odd considering that we're told repeatedly about how important it is to be a world leader in economy, technology, and security here is something that promotes all three and the pentagon's fat couffers are nowhere to be found. (well potentially compromises the third, but that's another story)
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Not exactly I am afraid. There are still huge issues to quantum computing. Namely isolation and data retrieval.
A quantum computer (or at least it's processor) needs to be totally shielded to the outside world while it operates as any interraction or mesurement from the outside world will break the theory. Also, at this moment, you cannot retrieve the processed data without interfering, right? So as soon as you get the data from one of the virtual processors working in 'other worlds', the thing breaks and you can't get anything anymore from it. So it's in fact pretty useless I'm afraid.
I don't think we're going to see a quantum computer in the years to come, and much less under our desks. Even if they were invented I believe our governments will keep them away from us as they could be quite mean to encryption.
No. The measurement destroys the entanglement.
The Tao of math: The numbers you can count are not the real numbers.
By "Pair off two electrons", I presume you mean put them in an entangled state where the spins of the two electrons are correlated? (For example, in the state |up, down> + |down, up>).
In that case, your system won't work. Putting one of the electroncs in this spin-flipping device would destroy the fragile entanglement. In other words, flipping the spin of one would do nothing to the other.
This is how it always is with entanglement -- entangled particles only remain entangled as long as you leave their entangled properties alone. Once you measure or modify the properties of one, the entanglement is ruined.
There's no reason for a sig here.
It means the spin does not yet have a determined value. And this can indeed be checked. There are probability inequalities (the so-called Bell inequalities, named after Bell who found them) which must hold if the result of measurement should be pre-determined for each particle. The laws of quantum mechanics violate those inequalities, and experiments by Aspect have shown that nature obeys quantum mechanics also in this respect (the violation of the Bell inequalities has been measured).
If those measured correlations mean interaction between those systems or not depends on which interpretation of quantum mechanics you prefer. Since there are interpretations where you don't need such an interaction, it's clear that you cannot use it to instantaneously transmit information with this effect (otherwise such interpretations couldn't possibly exist).
The Tao of math: The numbers you can count are not the real numbers.