By zapping diamonds with an enormous number of laser beam pulses, physics researchers have created several cases of what Einstein called "spooky action at a distance."
A team of scientists showed that two diamonds can entangle with one another, meaning that vibrations in one of the crystals share an invisible, long-range connection with vibrations in the other crystal.
"We have been able to demonstrate that even everyday objects can exhibit some of the strange, counterintuitive behavior of quantum physics," said University of Oxford professor Ian Walmsley, who led the study, published recently in the journal Science.
Until now, scientists had only seen that phenomenon in frozen clusters of atoms.
"One of the weird effects well-known from atomic-scale systems is the possibility of superposition – the ability of an object to be in two places at once," Walmsley said.
You may have heard of Erwin Schrodinger's cat thought experiment in which a cat is both alive and dead at the same time because its life depends on an atom that has both decayed and not decayed. This paradox illustrates how bizarre superposition can be.
In the case of Walmsley's study, photons were showing up in two spots at the same time and causing vibrations within a pair of diamonds. The researchers made it happen by placing two diamonds about 15 centimeters (about 6 inches) apart on a table and then shooting a series of photons at a device called a beam splitter. Most of them went toward one diamond or the other, but a few of the photons went both ways at the same time. When those multitasking photons struck the pair of diamonds, they caused vibrations called phonons with each of the crystals.
The light from each of the beams recombines after exiting the crystals. And sometimes when the light is leaving the crystals, it has less energy than when it entered. That's how the researchers could tell that the photon had caused some vibrations.
"We know that one diamond is vibrating, but we don't know which one," Walmsley said. "In fact, the universe doesn't know which diamond is vibrating – the diamonds are entangled, with one vibration shared between them, even though they are separated in space."
Walmsley said that diamonds may someday be used to generate random numbers or store information in next-generation computers, but his colleagues point out that this particular research project does not have any immediate technological applications. It's just really fascinating, and really confusing, at the same time.