# Tag Info

## Hot answers tagged notation

1

If your desired basis is the set ${|n\rangle}$, then the completeness relation tells you: $\hat{O} = \sum_a \sum_b \langle a|\hat{O}|b \rangle |a \rangle \langle b|$. Ideally, we prefer to do this in the orthonormal basis in which the operator $\hat{O}$ is diagonal, in which case this becomes \$\hat{O} = \sum_a \langle a|\hat{O}|a \rangle |a \rangle \langle ...

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