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Macroscopic Quantum Entanglement
meckardt writes: "We laugh at the science fiction of such programs as Star Trek, but it can almost be stated as a truism that what is fiction today may be science tomorrow and engineering next week. Researchers at the University of Aarhus in Denmark report in the science journal Nature that they have been able to cause particles to interact over a distance using lasers. The effect, called quantum entanglement, has been observed before, but never with such large amounts of matter. Don't expect transporters next week, but it is interesting that this report hits the streets the same day that Enterprise debuts."
I teleported home one night,
With Ron and Sid and Meg,
Ron stole Meg's heart away,
And I got Sidney's leg.
Consultancy: If you're not part of the solution, there's money to be made in prolonging the problem
XML causes global warming.
Think about it. Consider 2 polarized photons, 2 electron spins, 2 billiard balls, anything entangled such that a particular measurement performed on each always returns opposite results. When the system is set up, each object's probability of being, say, spin up, is 50%. The two spins are described by coupled wave functions, so that the 50% that corresponds to A being spin up also corresponds to B being spin down and vice versa. When one is measured, its wave function collapses into a single eigenstate, and its partner's wave function collapses into the other eigenstate. Thus, the final eigenstate of B is decided by the same measurement that measures the state of A.
This seems disturbing, the instantaneous change of B's wave function an arbitrary distance from A, when only A is being measured. But the simultaneous collapse of 2 coupled wave functions is mathematically no different from the collapse of a single wave function. When you have a particle with a large uncertainty in position, mesuring its position causes it to collapse to a single position eigenstate. If you have 2 detectors some distance apart, and use each to measure the presence or absence of the particle some very short time apart, you know that if you observe it at one, you won't observe it at the other. Say the detectors are 10m apart, and they take their measurements 1ns apart. If you detect the particle at the first one, you KNOW that the second won't detect it. But the 'information' about the wave function's collapse at the first detector would take 33ns to reach the second, if it travelled at the speed of light. So a single wavefunction's instantaneous collapse from all of space to a single point is just as much 'communication' as an entangled particle pair's simultaneous collapse.
So you have a choice: Either the entangled particles' behavior isn't that disturbing, any measurement of a quantum system is really disturbing.
Bugrit! Millenium hand and shrimp!