# More entanglement fun

StationZero
Q1: If every atom has to adjust their energy levels according to every other atom in the universe, does that mean that any given single atom has its interior invaded by a catalog of energy states from every other atom in the universe? And only after accounting for all the energy states that have already been taken, then find a unique one?

Q2: How can the spin states of two particles be measured 100's of miles apart when they trypically will interact with other particles almost immediately, for example in the pair creation of an electron and positron for the test system?

sheaf
Is Q1 inspired by the statements in Brian Cox's book and tv lecturs? If so, there is some relevant discussion here and on the physics stackexchange here

Gold Member
Q2: How can the spin states of two particles be measured 100's of miles apart when they trypically will interact with other particles almost immediately, for example in the pair creation of an electron and positron for the test system?

Particles can easily remain entangled even after interacting with other particles or fields. The question is whether the interaction collapses the state (at least in some basis) and in many cases that answer is no. For example, a magnetic field can alter the path of a charged particle without affecting its spin. If it was spin entangled before, it would remain spin entangled.

For photons: they can go through fiber cable and be twisted and turned without yielding any information about their polarization. Again, if it was polarizationentangled before, it would remain polarization entangled.

Q1: If every atom has to adjust their energy levels according to every other atom in the universe, does that mean that any given single atom has its interior invaded by a catalog of energy states from every other atom in the universe? And only after accounting for all the energy states that have already been taken, then find a unique one?
You'll notice they don't do this, of course. Every hydrogen atom in the universe has the same ground state energy, and each electron happily occupies its ground state without obtaining permission from the other ones! That's because they are different states: (ground state in atom 1) is a different state from (ground state in atom 2), and so the overall wavefunction has no trouble being antisymmetric.

StationZero

Every hydrogen atom in the universe has the same ground state energy, and each electron happily occupies its ground state without obtaining permission from the other ones!
That makes more sense to me, and yes I was talking about the Brian Cox show but I also found it here: http://www.youtube.com/watch?v=0x9AgZASQ4k&list=PL04722FAFB07E38E1&index=16&feature=plpp_video
These guys, though, seem to be saying explicitly that each atom has an entire catalog of every atoms energy state in the universe, and there's no budging on that. Am I reading this wrong?

StationZero
I guess my confusion is well-shared. I've been reading the Brian Cox thread. Very animated. Thanks for the lead Sheaf.

Confusion can be contagious.

Regarding the youtube video, note that "DrPhysicsA" is a professional musician, whose only current involvement in physics is producing this series of videos. The present one is legit until the 10 minute mark, at which point it takes off.

Try looking up "EPR Paradox" in Wikipedia. DrPhysicsA follows this discussion word for word, but then arrives at the wrong conclusion. Scroll down to where the article says "Here is the crux of the matter" and see if you can spot the difference.

StationZero
note that "DrPhysicsA" is a professional musician

Really? Brian Cox is a professional musician too! Maybe they should start a band called "the disentanglements" and write a song that clears up their shared miscommunications. I sure would like to hear it.:tongue:Yuk Yuk

San K
That's because they are different states: (ground state in atom 1) is a different state from (ground state in atom 2), and so the overall wavefunction has no trouble being antisymmetric.

in what way are the ground states different? ...even though they have same energy levels...