I am wondering what a circuit should look like if I want to prepare the state of the following form: $$ |0\rangle^{\otimes n} \mapsto \dfrac{ |1000\ldots0\rangle + |0100\ldots0\rangle + |0010\ldots0\rangle + \ldots + |00\ldots001\rangle }{\sqrt{n}} $$ Is this something well-known and trivial?
ANSWER
Apparently, this question was asked here.
The Q# realization is provided in katas 15-17 here.
Your state is a generalization of so-called W-state.
Here is a implementation of the state for three qubits.
You can also use method described in paper Transformation of quantum states using uniformly controlled rotations for preparing W-state with any qubits you want. When you use this method, set probability of states $|10\dots0 \rangle$, $|01\dots 0\rangle$,...$|00\dots1 \rangle$ to $\frac{1}{n}$ and probability of other states to zero.
