After we travel with the warp drive, we can be beamed up!
The Magical Behavior
Of Subatomic Particles
Moves Into Real World
January 6, 2006
Fridays, Sharon Begley writes Science Journal about the latest news and analysis from the front lines of scientific research. Sharon came to the Journal from Newsweek in 2002. She holds a B.A. in combined sciences, with an emphasis on physics, from Yale.
The most famous feline in science belongs to Erwin Schrödinger, or at least to his fertile imagination. A founder of quantum physics in the early 20th century, Schrödinger wondered what would happen if the seemingly magical behavior of subatomic particles occurred not only in the micro realm but also up here in the macro world. Which is how he found himself in 1935 with an imaginary cat that was both alive and dead.
Time was, physicists could blithely dismiss such Alice-in-Wonderland phenomena as irrelevant to the macro world. Sure, quantum physics allows paradoxical behavior such as particles that exist in two opposite states at the same time or that get over hills even though they don't have enough energy to do so. But once objects are much bigger than electrons or atoms, they behave. At least, they're supposed to.
In experiments unveiled last month, though, physicists managed to get quantum weirdness into larger systems than ever. In doing so, they have not only challenged conventional notions of reality but brought closer the day when quantum magic might find practical uses. Teleportation, anyone?
Schrödinger's imagined cat starts out alive in a box with a radioactive atom and a vial of cyanide. If the atom decays, the particle of radiation it emits smashes the vial, releasing poison gas and killing kitty. If the atom has a 50-50 chance of decaying by 11 a.m., and if you open the box then, is the cat alive or dead?
Quantum physics says that, at 11 a.m., the atom exists in both its decayed and not-decayed states, simultaneously. The reason is that the equation that describes the atom has two equally likely solutions, much as x²= 9 has two solutions (3 and -3), and you can't tell which one works until you try them. So with the atom. Until someone measures or observes it, it is both decayed and intact at once. Kitty, too, is therefore both alive and dead, in a condition called a superposition. As Schrödinger said, the living and the dead cat are "smeared out in equal parts." Only when someone peeks does she settle into being alive or dead.
Such quantum weirdness has launched a thousand philosophical treatises -- is there no reality until and unless someone looks? -- but at the end of the day it could be dismissed as a cute trick that didn't affect the real world, where atoms are definitely decayed or intact and cats are unambiguously dead or alive.
Unfortunately for realists, scientists at the National Institute of Standards and Technology in Boulder, Colo., scored a cat trick. They made each of six atoms spin in opposite directions at the same time. Each whirls like a top. But unlike any real top, the scientists reported in the journal Nature, each spins clockwise and counterclockwise simultaneously. (There is a charming animation of this at www.nist.gov/public_affairs/images/NIST_CatStates_embed.html1.)
The atoms had another strange property. They were "entangled." As I've written before2, entanglement is the "spooky action at a distance" that Einstein deplored, in which making a measurement on one particle in a cat state not only causes that particle to settle into one definite state but also makes related particles do the same. At NIST, observing one atom made it settle into a definite spin, clockwise or counterclockwise. And observing that atom caused the other five to pick a rotation, too.
Physicists at the California Institute of Technology, Pasadena, too, recently brought quantum spookiness into the macro world. They entangled two groups of 100,000 atoms some 10 feet apart. That is thousands of times more atoms than had ever been entangled before. "This shows for the first time that it's possible to entangle two massive, well-separated systems," says W. Jeff Kimble, who led the work.
Right about here is where I'm supposed to tell you that extending quantum magic into the macro world could pave the way for devices such as quantum computers, which would leave conventional computers in the dust. That is the NIST scientists' ultimate goal, says Dietrich Liebfried, who led the cat-state experiment. Because the elements of a quantum computer would exist in cat states, they could try many possible solutions at once, taking mere hours to crack the toughest codes (such as those used to encrypt financial data) and solve problems in which the number of possibilities explodes exponentially (such as finding the shortest or fastest airline and delivery schedules among multiple destinations).
But I confess that interests me less than what producing cat states and entangled particles says about the world. In an essay at the Web site Edge.org3, astrophysicist Piet Hut of the Institute for Advanced Study muses that quantum advances are making conventional understanding about what exists and what is real start "to melt away." With "avant-garde insights" such as entanglement, he writes, the next scientific revolution "could be a dissolution of the strict distinction between reality and fiction."
To which Dr. Liebfried adds, "I'm with Niels Bohr [a founder of quantum physics]. If you're not outraged by the implications of quantum physics, you don't understand it." |
