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In what ways would a coherent stream of matter waves/De Broglie wavelength interacting with the environment differ from a conventional coherent stream of photons? What have been observed and what have been proposed and/or theorized?

Here is a link to what I mean, as it seems it is not completely clear what I am talking about: https://en.wikipedia.org/wiki/Atom_laser

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  • $\begingroup$ Do you mean the free electron laser en.wikipedia.org/wiki/Free-electron_laser ? That system emits electromagnetic radiation and the differences are seen in the link. $\endgroup$
    – anna v
    Jun 12 at 4:59
  • $\begingroup$ Just updated the question to a link to what I am talking about. $\endgroup$ Jun 12 at 7:57
  • $\begingroup$ I think the wiki site emphasizes the similarities and differences all through. $\endgroup$
    – anna v
    Jun 12 at 8:53
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There are a number of differences between the two types, but they are also remarkably similar, the field of atom-optics outlines these. I will try and outline a number of differences that I can come up with.

Physical: There is a huge difference in particle flux. A BEC will typically contain around $10^6$ particles. This can be limited by the number of atoms loaded into the initial magneto-optical trap and the efficiency of the evaporative cooling. The number of photons in a laser depends on the power. For example, in our lab we use a 1W laser with a wavelength of 780nm, this gives a photon flux of $\approx 4\times10^{18}$s$^{-1}$. The propagation speed is also a difference, obviously photons in a laser travel at the speed of light. In contrast, the speed record for a BEC (from what I can find) is 28mm s$^{-1}$. Another difference could be the achievable coherence times.

Applications: There are a number of applications for both lasers and BECs, leaving out the obvious differences (BECs can't burn holes through solid objects) and focusing on an application that they have in similar, interferometry. There is much research and development in implementing interferometers that use BECs or matterwaves. This is due to the massive increase in sensitivity that can be achieved when using atoms instead of lasers with optical frequencies. This increase in sensitivity comes from comparing the energy of a photon at a frequency $f$ and the rest mass energy of an atom of mass $m$. For example, this ratio for a photon at an optical frequency and an atom of Rubidium comes out to be $\approx10^{10}$. However, the possible increase in sensitivity also depends on the particle flux, so this ratio is significantly reduced in practice.

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