There are many working quantum computers…

ah, I mean, working in the sense of OP: that a system which overcomes the "engineering hurdles" is actually feasible and will be successful.

To be blocked merely by "engineering hurdles" puts QC in approximately the same place as fusion.

	▲	adastra22 2 days ago \| parent [-]
		There are working quantum computers that are not only feasible, but exist, can be rented on the cloud, and are people pay money to use. Whether these are a commercial success at this point in time is missing the forest for the trees. A LOT of money has been put into getting as far as we have, and the limited market for using these machines at the moment means that getting a return on investment right now is difficult. But this is/has been true of every new technology. And quantum computers are getting better & more energy efficient year-by-year.