Decoherence can occur not only when a system is manipulated and measured, but by any interaction with the outside world, such as a slight vibration or a stray photon. My group is working on several possible solutions, one of which is encoding and error correction. If we assume from the beginning that errors due to decoherence will occur, then we can account for them and correct for them when we set up the system. Scientists are still debating the uses of quantum computers. Quantum computers will very likely be used for encryption programs.
Encryption uses the factoring of large numbers to restrict access to certain files and locations.
Classical computers take a very long time to factor large numbers since they operate on their bits one at a time, but quantum computers could do similar calculations with qubits in a matter of minutes, a fact that has caught the attention of the military. Quantum computers will also find a home in modeling quantum chemistry problems, since many of the variables in quantum mechanics are too complicated for classical computers. And many of the applications for quantum computers are not yet even known, according to David Bacon, a researcher in Whaley's group. As recently as the 1970s, no one had a clue that classical computers would be everywhere, from desktops and laptops, to chips in your toaster and microwave. I think the uses for quantum computers will become known as the field continues to advance.