Slashdot Mirror
Spintronics May Lead to Quantum Microchips
Rashan writes "A Scientific American article which waxes poetic about the possibility of microchips which use the "spin" of an electron to perform their functions." An excellent explanation of a complex subject.
Then a strange chip would be perfectly normal!
You are not the customer.
I'm afraid it is only spin.
sig is
Those of you who are interested in the future of alternative computing, including quantum computing, might want to check out Caltech's Computing Beyond Silicon Summer School program. The top minds from around the world will present the latest information about quantum, molecular, and DNA computing.
I'm glad I'm not the only one that recognizes just how cool QE networking would be. However, if the corps or gov get ahold of it first, it will be a bad thing. Incredibly bad.
QE transcievers by their very nature, are untraceable. Say you and I have a dialogue via anonymous email, and we agree to exchange a transciever pair. I go to Central Park at midnight, and pull the transciever pairmate out of a trashcan... we can network now, without knowing who the other is, or where they are. Chain 20 people together like that, and warez (just one example) would be unstoppable.
So, if you are part of the gov, how do you stop this? You make sure that eash QE transciever is built in such a way, that it can't be tampered with without unentangling. Then, you build a GPS reciever into it, connected to a second QE particle. It's pairmate will be in the Federal QE Network monitoring center... they'll be able to narrow it down to within a few feet geographically. It will allow them to sniff all traffic traveling through the QEnet, and will pinpoint where it is coming from.
You're infinite bandwidth will only be useful for a (nearly) infinite amount of advertising and some overpriced pay content.
The only hope we have, is that it's somehow simple to make your own QE transciever, and that someone anonymously publishes on the web just how to make your own. Make it underground.
Pun not intended.
Noticed something in that article - they state that the hard disk read heads use GMR sensors - not quite accurate. They use a single unit spin valve. GMR devices consist of many layers stacked on top of each other, and, more pertinantly, they operate at large magnetic fields. The sensor used have a lower field for peak sensitivity, and the change in resistance in smaller. GMR is conventionally used in the literature to indicate large, multi-layer devices. [0]
One thing that the article glosses over slightly is the difficulty in construction. Well, it's not so much a dificulty, as a paradigm shift. The metal GMR structures are built vertically onto a substrate, and thus the working current flows perpindicular to the plane of the substrate. This is distinct from traditional semiconductors, where the principle direction of the working current is parrallel to the plane of the substrate.
The notable exception would be the spin FET, but they've not actually been built yet, so it's a little tricky to comment on.
One option that the article didn't mention is the possibily of generating a magnetic semi-comductor / metal by using a conventional magnetic insulator (such as NiO, MnO or Fe2O3), and dopeing, or otherwise adjusting the electrical properties [1].
My research is into combined ab initio and statistical mechanical models of ultra thin films of the magnetic insulators. Particularly interesting is what happens when a two atom thick layer of iron is put over an NiO surface - spin dependant electron transfer, which is interesting. All in all, most of my work is the blue sky / basic building block level.
My point is that the spintronic devices require a finre degree of control in construction - by thier nature, the magnetic structure is important. Oh, and as a kicker to this, the length scale for a defect in a magnetic lattice is around 20 or so times larger than it's affect on the electrical properties. Additionally, it seems likely (to me) that other routes to mass manufacture may have to be found.
In other words: These are going to cost more. Not just because they are new, but also because they are inherently more complicated devices that electronic semiconductore devices.
[0] Well, in PhysRev anyway. IEEE and similar may use a different nomenclature
[1] My calculations suggest that a layer of NiO 4 formula units thick, or thinner, will be a metal.
The transition from laboratory discovery to actual heavy industry usage of GMR-based devices in the recording industry has been incredibly fast. One of the only other technologies that has transferred this quickly from lab to industry was the transistor, and it is obvious how influential and revolutionary transistors were. This gives a brief indication of the relative influence spintronics may have on the industry.
make world, not war
No, they use Spin-dependent electrons. This is spintronics, in a nutshell.
Up until now, almost all electronic devices have made use only of the electronic charge. Ie, amplifying it, switching on it, transferring it, etc.
Well, in a subtle manner, there is spin dependence in the above, due to Pauli exclusion, but that's buried in the quantum statistics.
Remember the electron is a spin-1/2 fermion, and hence has two possible states for a measure of it's spin in any given direction. Spin is an inherent property of many particles, with no classical analog, but you can think of it roughly as an angular momentum. Spin is quantized, unlike a spinning top. A spinning top is a classical system, which can have any rotational speed from 0 to any positive/negative values. (Negative means opposite direction of spin as a positive value).
Since the electrons are quantized spin-1/2 particles, there are only two measures of the spin angular momentum that are valid. +-(1/2)hbar where hbar is the Planck constant. Thus, an electron can only spin one way or another, there are no intermediate values (including no zero value, so it's ALWAYS spinning). Also note that this spin doesn't really represent the electron spinning about it's own axis, it's an inherently internal concept that's is actually quite involved.
These two values of spin of an electron can now be exploited in new devices. Right now the goal is to make devices that can inject electrons of one value of spin, and make transistors that work only for certain values of spin, or preserve spin parity, etc. Quantum computation would work nicely here too because the two states of spin are a good basis for representing a binary digit.
I haven't read the Scientific American article, so I don't know if I'm just repeating the obvious or not. But I'm a graduate physics student right now, and I hope to eventually work on some applications of spintronics. It is a currently buzzing field with much potential.
make world, not war