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Technology

Spintronics May Lead to Quantum Microchips 103

Posted by michael from the where-she-stops-nobody-knows dept.
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.
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Spintronics May Lead to Quantum Microchips More

Spintronics May Lead to Quantum Microchips

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  • Use quarks instead! (Score:5, Funny)

    by Limburgher ( 523006 ) on Tuesday May 14, 2002 @04:55PM (#3519890) Homepage Journal
    Then a strange chip would be perfectly normal!
  • quantum computing?
    we already have that:
    fork()

  • sound like a good idea but... (Score:3, Funny)

    by dimitri_k ( 106607 ) on Tuesday May 14, 2002 @05:03PM (#3519955)
    I'm afraid it is only spin.
  • You'll have to take that magnet out of here, this is a 'no spin' zone.
  • How sensitive to electro/magnetic interference would such a chip be?

    In times when my neighbor can fry all my PCs with a home-made impulse gun I'd be more interested in a light-based chip.
  • Will us nerds who do tech support begin to be called spin-doctors by the press now?
    • I doubt it, conszidering us tech support nerds currently aren't called transistor-medics. I doubt tech support would be fiddling around with the individual electron paths of a computer.
  • Of course you will have to power it via the static electricity generated while using a hula hoop while wearing a polyester leisure suit.
  • ...where the executives used the spin of "stock options" to perform their functions.

  • I'm not familiar at all with the field, so here's a dumb question:

    If they are going to use electron spins to keep track of information, how are we to encapsulate the electrons, with other electrons? Didn't the article say that they affect all other electrons in the area?

    • If they are going to use electron spins to keep track of information, how are we to encapsulate the electrons, with other electrons? Didn't the article say that they affect all other electrons in the area?

      The article said that the spin is coherent within the channel as long as the ferromagnet is switched in the correct way. It also said that the spin alignment had very short coherence outside the field. Depending on the material and mechanism anywhere from a few picoseconds to a few hundred nanoseconds. The reason for the decoherence is as you stated. Spin alignment is adversely affected by magnetic and electric fields. Since surrounding electrons give off such fields, you get really short spin alignment times.

  • GMR heads use the spin of electrons to detect changes in the magnetic field on the surface of the discs.
    • 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.

  • What if... (Score:1, Offtopic)

    by Zen Mastuh ( 456254 )

    ...all the electrons stop spinning? What's a sysadmin to do?

  • Spintronics could mean the end of booting your computer. From the article [sciam.com]:

    More sophisticated storage technologies based on spintronics are already at an advanced stage: in the next few years, MRAM (magnetic random-access memory), a new type of computer memory, will go on the market. MRAMs would retain their state even when the power was turned off, but unlike present forms of nonvolatile memory, they would have switching rates and rewritability challenging those of conventional RAM.

    Think about what this means! You will be able to turn off your MRAM computer and when you turn it back on, you won't have to boot it. The computer (its memory) would be in the state in which you left it. Think of how nice that'll be!

    Of course, when Windows crashed everyday, you'd still have to boot it.

    • We've had this in laptops for ages. Of course not with MRAM, but the effect is similar. When the machine is put into sleep, the memory contents are copied into a swap partition, and picked up from there when you start up again.

      Of course something else must be done, for example with CPU registers. Interestingly, MRAM technology also holds the key to 'magnetic CPU' which maintains its state in the same way as MRAM. That way, you have in a single chip, CPU, RAM and harddisk functionality.

  • For a fairly detailed overview of quantum computers, see Brian Hayes' article "The Square Root of NOT" [sigmaxi.org].

    The mind boggles at the power of a quantum parallel CPU and that's before some smart arse overclocks it.

  • Quantum computer school (Score:4, Informative)

    by preternatural ( 322346 ) on Tuesday May 14, 2002 @05:55PM (#3520257)
    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 [caltech.edu] program. The top minds from around the world will present the latest information about quantum, molecular, and DNA computing.
  • Instead of 0s and 1s we'll have +1/2 and -1/2!
    • Actually you are correct. No more binary, but it will be 0, 1 and both 0 and 1 (superimposed).
    • With spin and charge we could do up0 right0 up1 right1 ! Quadral cool I wonder if 56err48k modems will actually be able to do 96k Does this technology allow for the electron to change directions as in up to down and left to right or just the binary up to right?
  • Megnetisation is the setting spin. In this technology they are taking about using a very small nmber of spins to do logic and represent data.

  • My field! (Score:5, Informative)

    by DarkMan ( 32280 ) on Tuesday May 14, 2002 @07:05PM (#3520696) Journal
    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.
  • "For instance, even the earliest computer hard drives used magnetoresistance--a change in electrical resistance caused by a magnetic field--to read data stored in magnetic domains."

    All earlier practical Hard Drives before the "discovery" of the GMR effect used Electromagnetic heads; wildly different practicalities than GMR heads. They were simple electromagnetic devices mounted on aerodynamic substrates; low impedance, wire wound affairs and definitely NOT magnetoresistive.

    Did I miss something in the spin and magnetism physics relationship??
  • ...the possibility of microchips which use the "spin" of an electron to perform their functions.

    I thought that was the basis of quantum computing? At least when I read about it 2 years ago it was..... called a qbit?
  • Everybody is talking about building quantumcomputers, but no one has thought of a way to stop the distorsion that occurs when making an electron spin. The are multiple ways to make it spin, on of them is using a magnetic field. This will influence the electrons nearby. Other methods do have the same effect. There are two ways to deal with this: 1. Find a method that will not create distorsion. So far, no one has been able to come up with a good solution. 2. Compromise the distortion in the software. This will reduce the extra speed, gained by using the quantum mechanics, to almost nothing. Therefor, untill we find a way to make the particles spin in one or two directions without influencing the others, we will not be able to use all the extra speed. Distorsion is not the only problem. The order in which the particles are made to spin will also influence the state of the particles. I didnt' read the article, so if this has been sad already, I'm sorry.
  • Only half kidding:

    Imagine that programs
    in a quantum computer can have bugs that
    disappear as soon as you try to observe them.

    In current programming there are sometimes problems that disappear as soon as you try to debug them, the disappearance apparantly caused by the interaction with the debugger program.

    These bugs are called "Heisenbugs".

    It just appeared to me that quantum programs could have actual Heisenbugs.

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