I have been following at a distance since a few years the development of Quantum Computers. One of the more controversial approaches to Quantum Computing is the one proposed by D-Wave. D-Wave is also the only company which claims to have a specialized version of Quantum Computer ready to sell, and actually they did sell at least one Quantum Computer to a consortium made by Google, NASA, and the Universities Space Research Association.

What it is not yet clear is if it is really a Quantum computer, and even if it is, if it gives any advantages with respect to traditional computers. There are quite some different opinions about this, and this IEEE Spectrum article tries to understand where we stand now.