Physics and magic aren't often mistaken, but increasingly, physicists themselves seem to be trying to change that. Last year, a team at the University of California, Berkeley, announced that it had developed materials that could lead to an invisibility cloak. Last month, a group of researchers at Harvard University and the National Institutes of Health reported that it had accomplished something not unlike levitation, causing a microscopic sphere of gold to rise above a glass surface. Now, according to a paper published in the Jan. 23 issue of Science, a team of scientists from the Joint Quantum Institute (JQI) at the University of Maryland and the University of Michigan has joined the fun. The current bit of legerdemain? Teleportation.
Depending on your favorite sci-fi yarns, teleportation is either a very, very bad idea (see: The Fly) or a very, very cool one (see: Star Trek). For scientists, it's just very, very complex, so much so that at this point, teleportation is not a matter of moving matter but one of transporting information. Already, physicists have been able to exchange information between light particles — or photons — or between atoms, so long as they were right next to each other. The current experiment marks the first in which information has traveled a significant distance — 1 m, or a little more than 3 ft. — between two isolated atoms. It's also the first time the powers of a photon, which is good at traveling over long distances, and an atom, which is prized for its ability to retain information, have been jointly exploited.
Using a pair of ions, or charged particles, group leader Christopher Monroe and his team place each in a vacuum and keep them in position with electric fields. An ultra-fast laser pulse triggers the atoms to emit photons simultaneously. If the photons interact in just the right way, their parent atoms enter a quantum state known as entanglement, in which atom B adopts the properties of atom A even though they're in separate chambers a meter apart. When A is measured, the information that had been previously encoded on it disappears in accordance with the quirky rules of the quantum world. But all is not lost: because B is entangled with A, B now contains the information that was once carried on A. That information, in a very real sense, has been teleported.
O.K., so parents might not be inviting the JQI team to perform at their kids' birthday parties anytime soon, but what the quantum trick lacks in showmanship, it makes up for in practical applications for future computers. In 1965, Intel co-founder Gordon Moore predicted that the number of transistors that could be placed on a computer chip would double every two years — which is precisely what has happened. He was rewarded for his prescience with a sort of immortality: the famed "Moore's Law" is one of the venerable truths of the computer world. The rest of us were rewarded with ever faster and ever smaller computers. At some point soon, however, miniaturization will reach a point that's too tiny to be practical. It's then, many hope, that what's known as quantum computing — based on information-sharing particles — will take over.
Quantum-computing technology is currently being used to encrypt data, but it holds a lot more potential than that, if only because of its massive information-storage capacity. One of the marvelous little wrinkles of the quantum world is a condition known as superposition, in which a particle can occupy two states at the same time. (Don't ask; it just can.) For this reason, a quantum bit, or qubit, can store two numbers at once. Each qubit added to a quantum computer doubles the size of the system, so if you want to know the capacity of a computer that contains 300 qubits, take the number 2 and multiply it by itself 300 times. "That's more than the number of particles in the universe," Monroe says. (See the best inventions of 2008.)
The next step for the JQI team is to improve the photons' precision and the rate of communication between the particles. What we won't see soon — or ever, according to Monroe — is a contraption that can teleport humans from one point to another. Sorry, Captain Kirk, but beaming up is a pleasure strictly reserved for atoms. "There's way too many atoms," says Monroe. "At the other end of the transporter, you need to have some blob of atoms that represents Captain Kirk but has no information in it. I mean, what would that look like?"
No comments:
Post a Comment