Quaise Energy, a spin-off from the Massachusetts Institute of Technology (MIT), for example, are aiming to drill holes as deep as 12 miles (20km) to access temperatures of 500C (932F) or more. To do so, they are turning to a tool that draws on years of research into nuclear fusion power. "While others are putting shovels in the ground, we're putting microwaves in the ground for the first time," says the company's co-founder Matt Houde. 

He and his colleagues are experimenting with millimetre-wave directed energy beams that vaporise even the hardest rock. It focuses high-powered beam of radiation similar to microwaves but at a higher frequency onto a segment of rock, heating it up to 3,000C (5,432F) so that it melts and vaporises. By directing the beam so it bores through the rock, holes can be created without the debris and friction created by traditional drilling techniques.