The big near term milestones will be a demonstration of quantum computational supremacy (performing a computation on a quantum processor that takes much longer to compute using conventional high-performance computing), a demonstration of quantum advantage (demonstrating that a quantum processor can perform a -useful- computation faster than conventional computing resources) and a demonstration of fault-tolerance with active error correction. I would expect each of these to occur within the next ten years, and probably within the next five. The demonstration of quantum computational supremacy is likely to be the first to occur, and is likely within the next two years. Within fifty years, I would certainly expect quantum computers to be much more similar to todays computer architectures in terms of having multiple components dedicated to different functions (processing, storage, communication) and in terms of being used as general purpose computing devices rather than single purpose co-processors.
– Dr. Joe Fitzsimons, Principal Investigator, Centre for Quantum Technologies; Founder, Horizon Quantum Computing