Controlled Nuclear Fusion has been achieved by a variety of means, either by electrolysis, lasers or controlled fission, which requires vast amounts of energy - about one year's production of the Hoover Dam in less than a few seconds. To scale this down to power small devices such as a computer would be stupid, you can't contain it. Even if you have 1 mililiter of triterium (Hydrogen-3, the main component of Hydrogen fusion processes) fused, you'd still take out about 1/32nd of New York City, and render half of it unsuitable for living. Fusion creates loads of nuclear waste, generally from the surroundings where the fusion occurs, extreemely dangerous, and practically created the elements with the atomic numbers 90-98 in an enormous Hydrogen fusion bomb blast detonated above the Pacific Ocean. It is not safe, and impossible to use in smaller devices. This has been asked before, my answer will always be the same.