Monday, June 2, 2008

Here's something interesting the phenomena known at Quantum Entanglement looks to be more robust than ever.

Quantum entanglement stronger than suspected

Pairs of photons linked by the weird quantum effect of entanglement can pass through sheets of metal without the entanglement being destroyed. The finding means the quantum linking of particles is far more robust than scientists thought and could help them develop new ways of making quantum computers.

Scientists think quantum computers could be hugely powerful because of their ability to perform many calculations at once, instead of doing one after another like regular computers.

When photons are entangled, the physical properties of one are intimately linked to the other. Measuring the properties of one will instantly tell you the properties of the other. But many scientists believed entanglement broke down if the photons ever interacted with anything.

Now, Erwin Altewischer and his team at Leiden University in the Netherlands have shown this is not true. They used a crystal to split photons into pairs of lower energy photons with different and entangled polarisations. They then fired these entangled photons at gold sheets thick enough to block light.
Surface waves

The sheets were peppered with holes 200 nanometres wide. Although the holes were too small for light to squeeze through, Altewischer found the photons created waves of electrons on the gold surface called plasmons that passed through the holes and re-emitted the photons on the other side. Measurements showed that the emitted photons were still entangled.

"It's a good omen, because it's saying quantum entanglement can survive when you might not expect it to," says Bill Barnes, a photonics expert at the University of Exeter. "If they can survive this, what else can they survive?"

Altewischer says the fact that the entanglement is preserved, even when the light is converted into electron waves, means it could be used to develop new types of quantum computer or quantum cryptography systems.

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