Why haven’t we got useful quantum computers yet?

Alex Wilkins in New Scientist:

Quantum computers have long promised to solve certain problems faster than any ordinary, or classical, computer can. In fact, Google delivered on this promise in 2019, when it declared that its quantum computer had achieved quantum supremacy, performing a calculation impossible for the best classical computers of the day. As New Scientist said at the time, Google had “secured yet another place in the history books”.

Yet the next chapter of the quantum revolution is struggling to be written. Since Google’s breakthrough in 2019, other groups have made similar claims, but in each case improved algorithms for classical computers have reasserted dominance over quantum machines, or at least threatened to. With this back and forth ongoing, will quantum computers ever pull ahead?

More here.