Two Diamonds Get Quantum Entangled, Physicists Report

Atoms are governed by the strange laws of quantum physics---they can communicate across long distances, teleport, and perform myriad other acts that sound straight out of science fiction. But although we're made up of atoms, we can't do any of that stuff. We're governed by the laws of classical, or Newtonian, physics, where there's no teleporting allowed. How many atoms have to get together for classical physics to take over? Many physicists would dearly like to know, and, in an effort to suss out just when the change-over happens, have set up numerous experiments in which they watch for signs of quantum behavior in ever-larger objects, from molecules to nanoscale slivers of metal. But a paper published this week in Science takes the cake. Researchers report that they have observed entanglement in two three-millimeter-wide diamonds.Entanglement is one of the stranger properties of quantum objects. Entangled items are intimately linked, so that whatever happens to one of them somehow (we don't know how) affects the other. For a technical explanation of how the experiment worked, check out John Matson's coverage at Scientific American, but, in essence, the researchers set the diamonds vibrating and then poked them with a laser so they would emit a packet of vibrational energy. They were able to show that the packet did not come from one diamond or the other but from both, a sign that entanglement was at work. And what's more, the diamonds were at room temperature, a real oddity in a field where most objects have to be supercooled or put in other extreme situations for quantum properties to be observed. Although the entanglement didn't last long (only 7 picoseconds), the fact that it was in large objects at normal temperatures is pretty cool.