Entanglement adopted from the Book "Entanglement" by A. D. Aczel
Entangled entities (particles or photons) are linked together because they were produced by some process that bound them together in a special way. For example, two photons emitted from the same atom as one of its electrons descends down two energy levels are entangled. While neither flies off in a definite direction, the pair will always be found on opposite sides of the atom. And such photons or particles, produced in a way that links them together, remain intertwined forever. If one is changed, its twin - wherever it may be in the universe - will change instantaneously.
In 1935, Einstein, together with his colleagues Rosen and Podolsky, considered such entanglement just too spooky to be true: measuring one particle could instantly change the properties of another particle, no matter how far apart they are. EPR claims that there must be some hidden variables that are responsible for “non-local” force at a distance. If quantum mechanics allowed such bizarre effects to exist, then something must be wrong, or incomplete, as they put it, about the theory.
John Bell showed mathematically that the “EPR Paradox” was not a paradox at all. In 1964, he published his “Bell Theorem,” which showed that Einstein’s ideas about causality and locality are incompatible with the predictions of quantum theory and he showed that non-locality is an important feature of this world. Non-locality means that something that happens to one particle does affect, instantaneously, what happens to the second particle, no matter how far it may be from the first one.
Then, in 1972, two American physicists, John Clauser and Stuart Freedman, produced evidence that entanglement actually exists. And a few years later, the French physicist Alain Aspect and his colleagues provided more convincing and complete evidence for the existence of the phenomenon. Both groups followed the theoretical work by John S. Bell and set out to prove that the EPR thought experiment was rather the description of a real phenomenon.
Quantum theory has forced us to make radical conceptual renewal, which also lays a foundation for us to re-validate many of our traditional perception of our inner world. In the example of EPR experiment, we had to wait until 1972 to accept a strangest mysterious phenomenon of non-locality as an intrinsic quantum effect, which even Einstein could not imagine to be a possible reality.
What does entanglement mean? Entanglement breaks down all our conceptions about the world developed through our usual sensory experience. These notions of reality are so entrenched in our psyche that even the greatest physicist of the twentieth century, Albert Einstein, was fooled by these everyday. To understand, or even simply accept, the validity of entanglement and other associated quantum phenomena, we must first admit that our conceptions of reality in the universe are inadequate.
Entanglement teaches us that our everyday experience does not equip us with the ability to understand what goes on at the micro-scale, which we do not experience directly. Notions of causality and of the impossibility of being at several locations at the same time are shattered by the quantum theory.
For to understand entanglement, we creatures of reality depend on "elements of reality," as Einstein demanded, but as Bell and the experiments have taught us, these elements of reality simply do not exist. The alternative to these elements of reality is quantum mechanics. But the quantum theory does not tell us why things happen the way they do: why are the particles entangled?
How do we use this in Tao Philosophy?
© 2004-2005 Wayne L. Wang