realm of quantum
mechanics is the realm of physics at the atomic scale
This is a world in which an electron can be in two places
at once, in which an atomic nucleus can be spinning clockwise
and counterclockwise at the same time; in which matter
itself dissolves into a ghostly blur of possibilities as
soon as you try to look at it.
Indeed, the quantum world is so bizarre that even Albert
Einstein called it "spooky." And yet, quantum spookiness
is a very real and practical matter. The effort to understand
some of its more unusual consequences has led to number of Nobel
Prizes in the past two decades. And it has proven critical
to a host of 20 th century technologies, ranging from transistors
and lasers to atomic clocks and magnetic resonance imaging
A major question for physics in the 21 st century is whether
we can harness quantum weirdness for still newer kinds of
technologies—innovations that would amount to what
report from the National Academies of Science called
the Second Quantum Revolution.
Thanks to quantum mechanics for example, materials at
ultra-cold temperatures exhibit some very strange properties.
Perhaps the most familiar of these properties is superconductivity,
in which certain metals and other compounds acquire an ability
to transmit electricity with no loss of energy. Indeed, superconductors
have already found widespread application in devices that
require very strong electromagnets, such as MRI scanners
and high-energy particle accelerators.
In addition, there is a related property called superfluidity,
in which certain liquids are able to flow without friction.
Recently, NSF-supported physicists discovered a supersolid,
a kind of hybrid state in which some atoms can flow past
the rest of the atoms like a superfluid, without friction,
even as they are also sitting firmly frozen in place.
Finally, at the coldest of temperatures -- only billionths
of a degree above absolute zero -- quantum mechanics leads
to an even weirder form of matter called a Bose-Einstein
condensate. In the condensate, atoms and even entire
molecules lose their individual identities and occupy a single
quantum state. In other words, every atom is everywhere and
no single atom is anywhere.
Years of research are still required before superfluids,
supersolids and Bose-Einstein condensates find useful applications.
But one possibility being explored for Bose-Einstein condensates
computing, one of the most widely anticipated applications
from the quantum realm.
The circuits on today's computer chips can only shrink
so far before they run afoul of quantum-scale behaviors.
Rather than trying to circumvent those behaviors, however,
quantum computing embraces them by attempting to harness
some of the spookiest aspects of quantum mechanics. Through
quantum spookiness, for example, one object could be given
many values of the same property (a phenomenon known as superposition.)
Or many objects could be forced to share one property (a
phenomenon known as entanglement). Or both phenomena could
be made to happen at once.
Exploiting these strange behaviors is tricky, to say the
least. But if the challenges can be overcome, quantum computers
may be able to solve certain problems much faster than even
the most powerful conventional supercomputers.
Long before then, moreover, entanglement and superposition
may find practical application in other technologies. For example, Quantum
cryptography, has the potential to exchange
information with guaranteed secrecy; commercial products
already exist. Quantum entanglement may also permit more
accurate and better synchronized atomic clocks, which in
turn could improve GPS systems and mobile communications
And of course, that is just the beginning. Attempts to
tame the quantum realm are also opening up new possibilities
for nanoscience and other areas of physics, and are certain
to lead to technologies that today's physicists cannot even
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