Saturday, April 10, 2010

total connection under reality...,

Wired | Entanglement is one of the strangest consequences of quantum mechanics. After interacting in a certain way, objects become mysteriously linked, or entangled, so that what happens to one seems to affect the fate of the other. For the most part, researchers have only found signs of entanglement between tiny particles, such as ions, atoms and photons.

John Martinis and colleagues at the University of California, Santa Barbara looked for entanglement between two superconductors, each less than a millimeter across. These superconducting circuits, made of aluminum, were separated by a few millimeters on an electronic chip. At low temperatures, electrons in the superconductors flow collectively, unfettered by resistance.

Despite each superconductor’s relatively large size, the electrons within move together in a naturally coherent way. “There are very few moving parts, so to speak,” Girvin says, which helped the scientists spot evidence of entanglement. “It’s a general fact that the larger an object is, the more classical it is in its behavior, and the more difficult it is to see quantum mechanical effects.”

In the new study, researchers used a microwave pulse to attempt to entangle the electrical currents of the two superconductors. If the currents were quantum-mechanically linked, one current would flow clockwise at the time of measurement (assigned a value of 0), while the other would flow counterclockwise when measured (assigned a value of 1), Martinis says. On the other hand, the currents’ directions would be completely independent of each other if everyday, classical physics were at work.

After attempting to entangle the superconducting circuits, Martinis and his team measured the directions of the currents 34.1 million times. When one current flowed clockwise (measured as a 0), the team found, the other flowed counterclockwise (measured as a 1) with very high probability. So the two were linked in a way that only quantum mechanics could explain.

“It has to be in this weird quantum state for you to get those particular probabilities that we measure,” Martinis says. “The percentages of those different things are not something that you can classically predict.”

Finding entanglement between superconductors is “a fairly important milestone,” comments Anthony Leggett of the University of Illinois at Urbana-Champaign. The new study “does seem to be rather unambiguous evidence for entanglement.”