The 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 (MRI) scanners.

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 a recent 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 is quantum 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 networks.

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 fathom.

The Physics of Life and Mind [Next]