Physicists developing a quantum computer that’s entirely open source

Couldn't find any cost estimate, but from https://openquantumdesign.org/the-quantum-computer (scroll down to "What's Inside") I'm guessing 100's of k$ for the bill of materials (let alone keeping the thing going.)

So the "you" in "your own" has to have pretty deep pockets...for a relatively low fidelity 30 qubit device.

If you want to try quantum vibecoding, I threw up a site at https://www.haiqu.org where you can mcp with the quantum computer at TU Delft. Free, after you make an account.

This effort is likely aimed at industrial/academic entities and not "you" as in a single person. But anyway, it needs to be emphasized that the phrase "quantum computer" is today used to mean anything ranging from

-a useless machine that produces a signal indistinguishable from noise TO -a highly sophisticated marvel of science and engineering that performs otherwise impossible calculations

Many industrial quantum computers today fall closer to the the former category than the latter. A single person or small team with minimal funding has basically no hope of building anything meaningful.

I don't know of any other device that has such a broad range of quality represented under one name. Maybe like calling ELIZA and Opus 4.6 both "AI".

Do we have an example of a real quantum computer doing some kind of a computation that is not easily accessible by the regular computer?

I keep hearing about "the promise" and "achieving quantum supremacy" (again!), but is there a real example of a quantum machine doing something useful in real life?