When
You're a Ket Tune: "When You're a
Jet " (aka "Jet Song"), .
.
The "bra-ket"
notation was invented in 1930 by Paul
Dirac. The "ket", for example |B>, represents
the state of a quantum system. A "bra" is a "Hermitian
adjoint" of a ket (e.g. <A| is the bra version of
the ket |A>). The bra version basically means the same
thing as the ket version, but is expressed mathematically
in a way that allows us to take an inner product, e.g. <A|B>.
This gives
the probability amplitude for a particle in the state |B>
to transition to the state |A>. The somewhat silly terminology
of putting together a "bra", such as <A|, with
a "ket", such as |B>, to form a "bra-ket"
or "bracket", <A|B> is proof that physicists
do have a sense of humor! The tune for this song
is from Leonard
Bernstein's "West Side Story". Click here
to purchase the soundtrack from amazon.com.
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