@Astrum Have you studied linear algebra? It becomes a bit clearer after that.
Also, if you look at the concept of creation and annihilation operators -- that's something that's easily dealt with in the bra-ket notation but more tedious otherwise
The reason we need a distinction between the bra and the key is that at times you may multiply kets (happens often in quantum computation). For example, if you have two electrons; one with spin up and one with spin down, the overall state is |up>|up> (Also can be written as |up,up>)
This non-inner product of two vectors can be viewed as a vector in a new state space, though it's really a tensor
...or something like that
Anonymous
1:54 AM
@ChrisWhite: I didn't say that "TOE == quantisation"; I said, that a TOE must not onlyh unify matter and the forces and stuff, but also, must be quantised.
Anonymous
And I did say "edited" in the edit summary.
user54412
2:44 AM
@DImension10AbhimanyuPS I have high standards for tag wikis, yes, but I can afford to - if no one agrees with my vote, the edit goes through
user54412
and I have approved most of your edits that i've reviewed
user54412
@ManishEarth aka a "tensor product" :P
user54412
I personally love expanding |up>|up> into |up> \otimes |up> - when else to I legitimately get to use that symbol?
user54412
@CrazyBuddy I just skimmed the important bits
user54412
btw if you want to find the actual published paper, astronomers have their own abstract search service: ADS
user54412
2:50 AM
it's slower than google scholar, and it can't tolerate misspelled words, but it will search titles, authors, and abstracts and return a nice page with all the relevant info, including permalinks to the journal version, as well as arXiv links
user54412
@CrazyBuddy I have to compliment your English - it has improved a lot over the last year :)
One of my friends was studying quantum computation, and he got confused by the bra-ket notation. He came to me for help, it turned out that they were using all three ways of writing the product of two kets (which completely confused him because what was really just a change of notation seemed like the invocation of some magical theorem):
|1>|1> (You are a sensible person, who doesn't waste space but care about the meanings of notation. We will get along together splendidly) |1>\otimes|1> (You are a moderately sensible person who likes using extra space for writing the full notation. While this can make the equations stare back at you, you don't mind and plod on.) |1,1> (I hate you)
OK, flattening tensors into vectors isn't that bad, but it's annoying.
@Astrum Ah, nice. Yep, after applying it the notation starts making more sense. No need to stall QM till you learn L.A.
If you see this page, there are many "pending" tag synonyms. I' have noticed that very few people bother voting on tag synonyms. This post is like a request for people to vote on tag synonyms.
If you have at least 5 reputation on a particular tag (you can see how much reputation you have o...
@ManishEarth Can you please check, was there a deleted answer here?
2 hours later…
user54412
9:21 PM
Hmm, this came up in the first-posts queue, and I'm not too sure about what to do - it's link-only (bad), but to the correct answer on another SE site (good?), but for a question we'll end up closing because we shouldn't be giving out HW answers (bad), where the question was simultaneously cross-posted (huh?)
If you see this page, there are many "pending" tag synonyms. I' have noticed that very few people bother voting on tag synonyms. This post is like a request for people to vote on tag synonyms.
If you have at least 5 reputation on a particular tag (you can see how much reputation you have o...
