The main thing in quantum mechanics is that it operates with probabilities, not some exact values. Qubits could have a different probabilities being in 1 or 0,, not different levels or whatever.
For non-binary computers check Soviet tertiary computes of Setun family. They operated with trits, each could have -1, 0 or +1 state, or, in other terms true, unknown, false, or whatever. They was more effective than binary computers of the time, but development was shut down in 70s when binary computers was forced by unknown reason.
The main thing in quantum mechanics is that it operates with probabilities, not some exact values. Qubits could have a different probabilities being in 1 or 0,, not different levels or whatever.
For non-binary computers check Soviet tertiary computes of Setun family. They operated with trits, each could have -1, 0 or +1 state, or, in other terms true, unknown, false, or whatever. They was more effective than binary computers of the time, but development was shut down in 70s when binary computers was forced by unknown reason.