“All of the other use cases that people talk about are either more marginal, more speculative, or both,” says Scott Aaronson, a computer scientist at the University of Texas at Austin.
Until now, there has been good reason to be sceptical. Researchers have obtained only mathematical proofs that quantum computers will offer large gains over current, classical computers in simulating quantum physics and chemistry, and in breaking the public-key cryptosystems used to protect sensitive communications such as online financial transactions. “All of the other use cases that people talk about are either more marginal, more speculative, or both,” says Scott Aaronson, a computer scientist at the University of Texas at Austin. Quantum specialists have yet to achieve anything truly useful that could not be done using classical computers.