I think these tags should be kept. In my opinion a question talking about qubits can talk about more things than just their state: how to get qubits? (on-topic? Not sure), properties of qubits required for them to work, how to store qubits (on-topic? Not sure) and of course also about their states.
Whereas qubit-state is, in my opinion, only about questions regarding to the state of qubits.
You can probably be an expert knowing everything about the possible states of qubits and know nothing about how to get/produce them.
That is why I am thinking that we should keep both tags, maybe add to the excerpt of qubit that questions using this tag should have at least one other tag like qubit-state, qubit-production...
A draft for the new excerpt is this:
For questions related to quantum bits. Please add at least one more specific tag to specify the precise problem (e.g. [qubit-state] or [qubit-production]). Also try to indicate whether you're interested in theoretical or 'implementation' results.