I’ve read this article and watched the associated video. Some incredible claims are made like,
OK, so they built a structure of 300 crystal atoms, but was that the easy part? I understand a quantum computer is different than a classical computer, but how do you feed it equations? How do you program the computer? What would be the next steps to take this to the next level?
If I’m understanding it correctly, what they’ve built isn’t a general-purpose computer but a “simulator”- something like the equivalent of an analog computer. IOW, when trying to determine how a complex quantum system will behave, you could either go back to the fundamental math and try to calculate it- very difficult-, or you can set up some quantum qubits in a way that models what you’re trying to calculate and just let it do it’s thing and see what the result is.
The reporting of this one does annoy me. The actual interview, and article on the Sydney Uni site are very careful, and accurate. Beyond that the popular reporting has badly missed the point.
A neat, and clearly usually ignored bit from the article.
A wind tunnel can create understanding of aerodynamics that no current supercomputer can match. However we don’t claim that the wind tunnel is more powerful computer than a supercomputer. As Lumpy writes - the quantum system is a simulation of what is being studied. Systems that are amenable to simulation by the quantum system built. So unlike a wind tunnel (which is a laboratory version of the actual system being studied) the physics is modelled in a different domain. An analog computer versus the real thing is a good example. (Most people have never stumbled upon an analog computer however, so the relationship is still hard for most to grasp.)
The calculation of the size of an equivalent conventional computer comes from the combinatorial explosion of possible states the system can represent. This is a favourite trick for almost any physical system. Just calculating the exact result of the first break on a snooker table is nearly as bad.
As for how this system is ‘programmed’, it uses electromagnetic fields (some to create the array, and lasers to control other aspects) to set up the simulation how they want it it. You can read a more detailed, but still brief, article here. Presumably the fields and lasers are actually controlled by a ‘traditional’ digital computer.