Quantum computing is going to make it possible to solve problems that normal computers simply cannot do.

Most of these are optimizing problems like “compute the best solution to traveling salesman” or “find a molecule that binds to this receptor”.

On normal computers solving such problems “perfectly” takes^exponential^ amount of computing time vs. the size of the problem.

Quantum computers are going to chop down that exponential thing a little, so we can see the results before the sun burns out. The reason QCs are theoretically able to do this is that each added qubit improves the machines performance exponentially.

However, the qubit state is so fragile that we need hundreds of them to make a single “stable” logical qubit that can do operations repeatedly. What the quantum computer uses as qubit (photons, super-conducting wire) is irrelevant as long as the system can do useful work.

Because of the fragility, the results are gathered using thousands of runs on the quantum machine and measured statistically.

We are not quite there yet to solve any useful sized problems.