Antimatter Galaxies/Universe

[neufer]

Quantum statistics define the term "indistinguishable" not humans.

Nonsense! There are many different meanings for "indistinguishable", and all are defined by humans.

As regards to elementary particles there is only one meaning for "indistinguishable."

Two indistinguishable elementary particles must be in an:

1) antisymmetric quantum wave state if they are fermions or in a
2) symmetric quantum wave state if they are bosons.

The particular definition you are using here is just one, and isn't the one I'm using (again, this shows why the term is likely to create confusion). Electrons are indistinguishable in the sense that there are no differences at all in any physical properties between them. Photons are not indistinguishable in this sense: every photon in the Universe may have slightly different physical properties, and with good enough measuring equipment each could be distinguished from the others. Yet another meaning, which is the one most of this discussion has concerned, involves distinguishing between types of entities. An individual photon and antiphoton are potentially distinguishable, because they have different physical properties (such as energy). As a class, photons and antiphotons are not distinguishable, because there is no property class of one that isn't shared by the other- because they are the same type of particle. It is all these different meanings of "indistinguishable" that make it a poor choice of wording in the original statement.

Free photons may have infinitely many energy states & momentum directions
but just two different spins for each direction just as free electrons have.

Coherent laser photons (all with the same energy state, momentum direction & spin state)
are "indistinguishable" just as a coherent beam of polarized electrons are.

[Chris Peterson]

As regards to elementary particles there is only one meaning for "indistinguishable."

Sorry, that is simply not the case. Two completely different particles may be indistinguishable simply because we lack the tools to distinguish them. That's perfectly valid usage, and demonstrates why the term needs to be qualified if the context doesn't make the intended meaning completely clear. I'm not arguing that there's anything wrong with the definition of "indistinguishable" that you are using, only that there are multiple definitions of that word. Heck, my degree is in quantum mechanics, and I didn't read your first statement as using the meaning you are now offering. So there is definitely the possibility of confusion.

Coherent laser photons (all with the same energy state, momentum direction & spin state)
are "indistinguishable" just as a coherent beam of polarized electrons are.

The photons may be indistinguishable in the sense that we can't measure the difference between them, but they are not indistinguishable by the QM definition you are using, since the photons will not have the same energy state, they will simply all be very nearly the same energy. Each will have a different history that can and will affect its energy level. No laser is perfectly monochromatic.

[neufer]

<<A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of weakly interacting bosons confined in an external potential and cooled to temperatures very near to absolute zero (0 K, −273.15 °C, or −459.67 °F). Under such conditions, a large fraction of the bosons occupy the lowest quantum state of the external potential, and all wave functions overlap each other, at which point quantum effects become apparent on a macroscopic scale.

This state of matter was first predicted by Satyendra Nath Bose and Albert Einstein in 1924–25. Bose first sent a paper to Einstein on the quantum statistics of light quanta (now called photons). Einstein was impressed, translated the paper himself from English to German and submitted it for Bose to the Zeitschrift für Physik which published it. Einstein then extended Bose's ideas to material particles (or matter) in two other papers.

Seventy years later, the first gaseous condensate was produced by Eric Cornell and Carl Wieman in 1995 at the University of Colorado at Boulder NIST-JILA lab, using a gas of rubidium atoms cooled to 170 nanokelvin (nK) (1.7×10−7 K). For their achievements Cornell, Wieman, and Wolfgang Ketterle at MIT received the 2001 Nobel Prize in Physics.

Velocity-distribution data of a gas of rubidium atoms, confirming the discovery of a new phase of matter, the Bose–Einstein condensate.

Left: just before the appearance of a Bose–Einstein condensate.
Center: just after the appearance of the condensate.
Right: after further evaporation, leaving a sample of nearly pure condensate.>>