- #1
Juqon
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Homework Statement
What are the conditions so that the matrix [itex]\hat{p}[/itex] describes the density operator of a pure state?
Homework Equations
[PLAIN]http://img846.imageshack.us/img846/2835/densitymatrix.png
[itex]p=\sum p_{j}|\psi_{j}><\psi_{j}[/itex]
The Attempt at a Solution
I know that tr([itex]\rho[/itex])=1 for pure states.
But I do not know how to construct the density matrix. Or is it [itex]\hat{p}[/itex] already?
In my book, there is the example "hermitian, tr=1, [PLAIN]http://img89.imageshack.us/img89/4346/densitymatrixexample.png", but I do not know how they constructed that.
Maybe I can just say a+d+e=1; c,b arbitrary?
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