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Bras and Kets

  1. Jul 31, 2008 #1
    I began my physics study about one year ago and learned all of classical mechanics in that year; but I am now studying Quantum Mechanics. The book I'm using (Dirac's Principles of Quantum Mechanics) Introduces Bra-Ket notation in the first chapter rather concisely. I understand the mathematical basis of the Bras and Kets, but what is the physical interpretation of them?
  2. jcsd
  3. Jul 31, 2008 #2
    Its a representation. Why does it need a physical meaning? Maybe a wavefunction, if you consider that physical.
  4. Jul 31, 2008 #3
    I suppose I used the wrong word... What does it represent? and how?
  5. Jul 31, 2008 #4
    A ket vector describes a system in state space but, like so many things in quantum mechanics, I'm not sure you could attach a 'physical interpretation' to them.

    Of course if you wanted, I suppose you could use ket vectors for your usual 3-dimensional mechanics problems in which case [tex]\left|\alpha\right\rangle = \left(x\:y\:z\right)^{T}[/tex] could represent any physical vector quantity you like?
  6. Jul 31, 2008 #5
    Basically, the complex number <out|O|in> is the amplitude to start from state |in> and end up to state |out> via the operator O.

    But mathematically, <V| is the dual form to vector |V>.

    Excellent choice of book. Keep up with it, it's worth. You'll need to wait a little bit. Later in (12) "The general physical interpretation"
    Last edited: Jul 31, 2008
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