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I have been reading about quantum entanglement, and I was wondering what quantum states can be "sent" using entanglement. I know you can measure the spin of one of the particles, and know the spin of the other, but can you also do this with other quantum states, such as polarization, or energy?

Also, could you theoretically entangle molecules, or even larger structures? What is happening in this field of physics?

Finally, if you were able to measure the energy levels of the entangled particles, when you changed the energy state of one of the particles, would the other? Could this violate the first law of thermodynamics, or is the change so small that it does not matter, since this is the quantum world?

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Any quantity or measurable property of any particle or any physical system may be entangled with any property of another system (or with any other commuting property of the same system). Decoherence is what practically "measures" these quantities before you want to and any measurement of a quantity destroys its entanglement with other quantities. So too large or too hot or too strongly interacting systems will effectively not stay in an entangled state for too long. However, degrees of freedom positioned at systems that are macroscopic have already been made entangled. –  LuboŇ° Motl Sep 5 '13 at 16:17
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Some related papers on experimentally measuring entanglement for molecules and larger stuff: bucky-balls‌​, more bucky-balls, small diamonds –  Glen The Udderboat Sep 5 '13 at 16:29

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