Tuesday, June 10, 2008

Tangled up in Quantum

Scientists perform experiments in order to test a theory. If enough data is generated to support a claim, that claim is usually declared true. But what if the experiment continuously gave a predicted result only because the scientist was on earth? Perhaps a different outcome occurs in space.

This is the argument behind a recent proposal to launch a mission called Space-QUEST (Quantum Entanglement for Space Experiments). Anton Zeilinger of the University of Vienna submitted the proposal to the European Space Agency. He wants to perform quantum entanglement experiments for the first time in space, at the International Space Station (ISS).

Quantum entanglement describes the complex way particles are linked together, such that one cannot exist without the other, regardless of distance. Superposition, the ability to get two different but related measurements, is central to an understanding of quantum entanglement.

According to quantum theory, measurements made on linked particles, no matter how far away, are instantaneously influenced by one another. Einstein notably poked fun at the idea of instantaneous influence, labeling it "sooky action at a distance", as it violated certain predictions of special relativity. He disliked and dismissed quantum entanglement entirely. This is summed up in the EPR paradox, a thought experiment by Einstein, Podolsky, and Rosen.

But numerous short-distance experiments on earth have agreed with quantum theory and provided strong evidence of quantum entanglement. The experiments involved sending two entangled particles, for example photons, to separately located scientists, who then take measurements. Despite this, there are some who believe that the results are a false positive. Quantum entanglement may only work on earth, where distance is limited. Maybe something different happens to entangled photons over enormous ground-to-earth distances. Zeilinger is determined to find out.

Since he's already proven that single photons can be detected on the ground by bouncing them off orbiting satellites, he plans to separate two entangled particles at a distance never before tested, one particle to an orbiting astronaut in space (At the ISS), and the other somewhere on the ground, here on Earth. Maybe Einstein will be proven right.

And yes, the title alludes to tangled up in blue (arguably my favorite Dylan song).

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