David Deutsch is the founder of the field of quantum computation. Paul Benioff, Richard Feynman, and others had written about the possibility of quantum computation earlier, but Deutsch’s 1985 paper on Quantum Turing Machines was the first full treatment of the subject, and the Deutsch-Jozsa algorithm is the first quantum algorithm.
When he first proposed it, quantum computation seemed practically impossible. But the last decade has seen an explosion in the construction of simple quantum computers and quantum communication systems. None of this would have taken place without Deutsch’s work.