Matrix element from eigenvectors

[vali...@gmail.com]

Hello,

This may be a very easy question to answer, but I can't find any example in the documentation of QuTiP.
I am trying to calculate the expectation value of a certain operator Q with the eigenvectors of a Hamiltonian H. I do

evals, evecs = H.eigenstates()

How can I use the function Q.matrix_elements(bra, ket) from evecs? Basically I don't know how to select a given eigenvector from evecs and transpose it. My attempts so far failed.

Thanks a lot for the help!

Best,

Pol

[Morgan Hedges]

Hi Pol,

you take the Hermitian adjoint of a ket using it's "dag" method.

To calculate the matrix element between the 5th eigenvector  and some ket "K", you can do

    Q.matrix_element(evecs[4].dag(), K)

Is that what you had in mind?

Morgan