Bras and Kets

1. Jul 31, 2008

Reedeegi

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. Jul 31, 2008

K.J.Healey

Its a representation. Why does it need a physical meaning? Maybe a wavefunction, if you consider that physical.

3. Jul 31, 2008

Reedeegi

I suppose I used the wrong word... What does it represent? and how?

4. Jul 31, 2008

tshafer

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 $$\left|\alpha\right\rangle = \left(x\:y\:z\right)^{T}$$ could represent any physical vector quantity you like?

5. Jul 31, 2008

humanino

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>.

edit
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