Been following, sometime interacting with D-Wave for some time, a relatively optimistic update in Nature. Controversy remains.
D-Wave upgrade: How scientists are using the world’s most controversial quantum computer
Scepticism surrounds the ultimate potential of D-wave machines, but researchers are already finding uses for them. ... by Elizabeth Gibney
How does it work, how is it different? In Nature:
" ... Unlike other quantum computers, D-Wave is suitable only for solving certain tasks, known as optimization problems. To find optimal solutions, researchers first put qubits, made of superconducting loops, into their lowest energy state, in which each is in a quantum superposition of both ‘on’ and ‘off’. Magnetic fields that represent the problem then gently nudge this state towards a new one — a process known as quantum annealing. The state evolves while maintaining its low energy such that when it eventually ‘collapses’, it should leave qubits in the best configuration for solving that problem. Because the system sifts every possible answer at once, in theory it could be a faster way to resolve problems that, when solved classically, get exponentially harder with each added variable. But posing research questions in a form that the machine can handle often means using several qubits to represent a single variable, limiting the size of the problems it can handle. ... "