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Spintronics and Quantum Computation
The integrated circuits in a computer system are made possible by utilizing the charge degree of freedom of electrons in semiconductors, whereas the information storage is implemented using the spin degree of freedom of electronics in magnetic materials.The area of electronics that uses both degrees of freedom is now being called spintronics.
Already, spintronics has yielded a couple of uses and may eventually provide the underpinning for computers that employ quantum mechanical efforts to perform calculations. "If you can manipulate the spin, it gives you another parameter to play with, " said Dr. Mark Johnson, a research scientist at the Naval Research Laboratory in Washington. At the Spintronics 2001 conference in Washington, one of the first devoted to the topic, scientists reviewed their achievements and the gaping challenges. A couple of years ago, an early application of spintronics helped bulge the capacity of computer hard disks by making the part that reads data from the spinning platters much more sensitive to magnetic fields. "Everybody has a spintronics device on their desktop," said Dr. David D. Awschalom, director of the Center for Spintronics and Quantum Computation at the University of California at Santa Barbara. While improved hard disks and memory chips are useful, researchers in spintronics are still searching for something that will propel the field forward the way the transistor transformed electronics. "People have not come up with the killer application that will come onto the market tomorrow," said Dr. Sankar Das Sarma, a professor of physics at the University of Maryland. Most researchers in the field have the same distant goal: using spintronics to build computers that take advantage of the bizarre all-possibilities-at-once nature of quantum mechanics to perform divergent calculations simultaneously. Now Katie Pennicott, who is Editor of PhysicsWeb, wrote there an
article (April 24, 2002) called "Spintronics gets serious",
in which Friso Jedema, of University of Groningen, who published
with colleagues an article on the subject in Nature (2002 Nature
416 713) But Keneth Chang has something to say about spintronics and quantum
computation: "While improved hard disks and memory chips are
useful, researchers in spintronics are still searching for something
that will propel the field forward the way the transistor transformed
electronics. 'People have not come up with the killer application
that will come onto the market tomorrow,' said Dr. Sankar Das Sarma,
a professor of physics at the University of Maryland. Most researchers
in the field have the same distant goal: using spintronics to build
computers that take advantage of the bizarre all-possibilities-at-once
nature of quantum mechanics to perform divergent calculations simultaneously.
Electrons can be thought of as tops that can spin clockwise or counterclockwise
but always at one fixed speed, and the spinning generates an intrinsic
magnetic field. Electron spins are in many ways ideal for representing
0's and 1's, the binary on-off language that computers use in their
calculations. If the spin , the orientation of the electron's magnetic
field, is pointing down, that can represent a 0. Flip the spin upward,
and that represents a 1. Two spins can then be 'entangled' with
each other, so that neither is distinctly up or down, but a combination
of the two possibilities, similar to the Schroedinger's Cat paradox
in which a cat is simultaneously alive and dead. And because the
spins exist in both states at once, a spin-based quantum computer
using the spins would, in theory, compute all possible answers in
one pass. A conventional computer has to make each calculation separately,
which can be much slower if there are many possibilities that need
to be checked. While quantum computers are probably decades away,
recent experiments have begun to fill in some pieces of the puzzle,
like how to line up the electrons' magnetic fields and how to flip
them around at will". Related news:
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When we open a computer, we see two critical functions realized
by semiconductors and magnetic material; the processing and the
temporary storage of information are carried out by semiconductor
integrated circuits, and the nonvolatile mass storage of information
is accomplished by magnetic storage devices. The integrated circuits
are made possible by utilizing the charge degree of freedom of electrons
in semiconductors, whereas the information storage is implemented
using the spin degree of freedom of electronics in magnetic materials.
Although so far used separately in most cases, the combination of
the two degrees of freedom can result in enhanced performance of
the existing devices. It may also make it possible to realize functionalities
not available by using only one of the two. The area of electronics
that uses both degrees of freedom is now being called spintronics.
