Bose Einstein Condensate

[steevey]

Ok, so they cool this substance so that all atoms occupy the lowest energy state, making them all in the same state, and also really close together. But, is that property caused by entanglement, or that because they are all so close together that all the particles wave functions are entangled, and if so, does that disappear when you observe it, or does it stay there because the waves are still all in the same state and technically interacting with each other at all points in time? Cause I've heard it being described as "you can now see the quantum effects on a macroscopic scale", but that pretty much defies my understanding of quantum mechanics.

Edited February 9, 2011 by steevey

[swansont]

The particles are in the same state, but they are not entangled. Entanglement means not knowing what state the particle is in.

[steevey]

The particles are in the same state, but they are not entangled. Entanglement means not knowing what state the particle is in.

 

So then how come when they are in the same state but have macroscopic distance between each other that they still act as one particle?

[swansont]

So then how come when they are in the same state but have macroscopic distance between each other that they still act as one particle?

 

To get to the lowest energy state means that the ensemble is very cold, so the deBroglie wavelength is large. Saying the particles are far apart loses meaning, because the wavelength is comparable to the separation distance.

[steevey]

To get to the lowest energy state means that the ensemble is very cold, so the deBroglie wavelength is large. Saying the particles are far apart loses meaning, because the wavelength is comparable to the separation distance.

 

 

But if entanglement collapses upon observation, I still don't get why when you look at it, all the atoms interact simultaneously and instantaneously as if they were one atom. Like if I shot one atom with a very low frequency laser, all the other atoms would act identically to that specific atom instantaneously.

Edited February 10, 2011 by steevey

[swansont]

But if entanglement collapses upon observation, I still don't get why when you look at it, all the atoms interact simultaneously and instantaneously as if they were one atom. Like if I shot one atom with a very low frequency laser, all the other atoms would act identically to that specific atom instantaneously.

 

That's not really a description of how a BEC would behave. "Acting as one atom" means the system is coherent, not that the entire system reacts to one being hit by a photon.