20 years from the first idea to working example, not 50, and was in scaled production only 10 years later. Perhaps would have been faster if vacuum tubes hadn't been so successful.
I think it's time to conclude that quantum computer is just significantly harder than transistors for computing.
That doesn't make sense at all. I think they were just showing that quantum computer advancement isn't going to have the same rapid development that transistor based computers did a few decades ago.
To be clear: I think investing money in making quantum computers that are intended to show better performance than supercomputers for a wide range of high performance computing tasks is unlikely to bear any useful fruit for the foreseeable future.
That doesn't mean I don't want investment into quantum optics, or any number of other quantum-related fields, which have demonstrated far more utility in far less time than quantum computing.
We have working single qubits today. Just not millions of them. Much of it has to do with investment. Previous govts poured a great deal of money into transistors. It's mainly private funding for quantum. Even private isn't the same scale as Bell Labs, adjusting for inflation.
I believe the decoherence times for atomic qubits (at least neutral atom) is much higher than that of trapped ions or superconducting, on the order of seconds.
