entangled diamonds

OTTAWA -- An Ottawa physicist's team has "entangled" two diamonds, bringing the mysterious world of quantum physics to objects big enough to see.

Entanglement is a process in quantum mechanics by which two objects act like a single object even though they're not physically connected.

It usually involves very small objects -- atoms or molecules, for example.

Now Ben Sussman of the National Research Council has entangled objects far bigger than molecules -- pieces of diamond about half a millimetre thick. It's a step toward extremely fast quantum computing.

Sussman and his group write that "our intuition about the natural world" says quantum physics rules the tiny scale of atoms, while "classical" laws of motion cover objects big enough to see, such as cars or golf balls.

Quantum physics has been stretched to larger objects already, but there are usually special circumstances. For instance, scientists have used ultracold superconductors isolated from their surroundings.

These diamonds are large and operate at room temperature, some 15 centimetres apart. Sussman said they could, in principle, be even more distant. (He used synthetic diamonds to avoid impurities, but natural stones would work too.)

Entanglement contradicts what our senses tell us. It means two distinct objects have a relationship where a change in one means a simultaneous change in the other.

Physicists sometimes use the analogy of a teeter-totter: When one end goes up, the other has to go down at the same time.

But entangled objects aren't physically joined like the teeter-totter's two ends.

Einstein didn't like the concept; he called it "spooky action at a distance." Still, experiments show it's real.

The quantum world has captured popular imagination for decades with its puzzles. There's Edwin Schrodinger's cat, where the principle of uncertainty says the cat may be alive and dead at the same time.

There are possibilities of teleportation and time-travel -- staples of science fiction that always want to bend reality. The concept of entanglement leads to dreamy notions that everything is connected to everything else.

Now the reality of quantum mechanics is leading toward a more matter-of-fact goal: computers faster and more secure than anything made today.

Sussman's group used diamonds because they react to laser light by showing some characteristics of the quantum world, and their extreme hardness helps preserve that quantum character.

"This (entangled diamonds) is a state that simply can't be described with classical physics," Sussman said.

"There's great interest in understanding the transition between this microscopic world of quantum mechanics and our macroscopic world, which we live in every day."

What the diamonds shared "is a bit ethereal," Sussman said. "They shared a deep connection. They shared a vibration. They shared the same state. In a sense, these two objects shared each other. They became one... It's a bit romantic, but could be suitable, given that they're diamonds.

"They're both about steps toward quantum computing and are really fascinating because we've been able to make all this microscopic quantum stuff exist at large sizes (millimetres) and at room temperature," he said.

"I've been using the idea of building on our 'quantum workbench' -- something quantum that you can really get your hands on."