One of the questions folks tend to ask me is some form of, "when can I expect my cellphone to contain a quantum co-processor?" That gives me an excellent opportunity to tell them everything that I know about cryogenic refrigerators (which only takes a minute).

The chips we make (speaking directly of D-Wave, but afaik this is true of all superconducting QC efforts) would cost pennies if we produced them at scale. But the surrounding machinery is extremely complex, and very expensive to manufacture -- and scale would only get you so far. My rough understanding of refrigeration is that the temperature differential strongly depends on the length of the heat exchanger. Qubits are famously sensitive to noise; and blackbody radiation gives an inescapable dependence between noise and temperature. In short, a miniaturized fridge would be necessarily hot, and therefore too noisy to perform quantum computation!

So the sad news is that, barring some major developments, we may never have miniature quantum computers. In the foreseeable future, hardware costs will be measured in millions of dollars. So even if you're a millionaire, you probably don't want to buy a quantum computer. If you work for a university, a national laboratory, or a major corporation, you might try to convince your organization to purchase a quantum computer. If you succeed in that pitch, you'd almost certainly need to share it with your colleagues over a network.

So to me, an industry insider, it feels that public access to quantum computing is almost necessarily QCaaS.