Quantum computing can in fact only offer an improvement in speed, given what is understood about the fundamental underlying physics. There is no algorithm a quantum computer can run that the computer you are using to read this cannot: https://en.wikipedia.org/wiki/Church%E2%80%93Turing_thesis
Quantum computing can in fact only offer an improvement in speed, given what is understood about the fundamental underlying physics. There is no algorithm a quantum computer can run that the computer you are using to read this cannot: https://en.wikipedia.org/wiki/Church%E2%80%93Turing_thesis