To date, several technologies are the leading contenders to produce a useful quantum computer. Companies have used them to build machines with tens to hundreds of qubits, error rates are reduced, and they have largely moved from worrying about basic scientific problems to solving engineering problems.
However, even at this seemingly late date in the development of this field, there are companies that are still developing entirely new qubit technologies, betting on the company that they have identified something that will allow them to scale in ways that will allow the story of what they couldn't. One of those companies recently published a paper describing the physics of their QBIT system, which involves lone electrons floating on top of liquid helium.
Captures single electrons
So how do you get an electron to float on top of helium? To find out, Ars spoke to Johannes Pollalanen, chief scientist at Eeroq, the company that carried out the new work. He said that this is actually old physics, with the first demonstrations of it being made half a century ago.
“If you bring a charged particle, like an electron, near the surface, because helium is dielectric, it will create a small image charge underneath it in the liquid,” Polalanen said. “There will be a small positive charge, much weaker than the electron charge, but there will be a small positive image there. And then the electron will naturally be associated with its own image. He'll just see that there's a positive charge and somehow they want to move towards it, but he can't get to it because helium is completely chemically inert, there are no free spaces for electrons to go.”
Obviously, extremely low temperatures are required to produce helium liquid. But it can actually remain liquid up to 4 Kelvin, which doesn't require the extreme cooling technologies needed for things like transmines. These temperatures also provide a natural vacuum, as almost everything else will also condense on the walls of the container.
The chip itself, along with diagrams of its organization. The trap is set with a gold electrode on the left. Dark channels allow liquid helium and electrons to flow into and out of the trap. And the bluish electrodes on the top and bottom read the presence of electrons.
Credit: eeroq
Liquid helium is also a superfluid, which means it flows without viscosity. This allows it to easily flow through tiny channels cut into the surface of the silicon chips the company used for its experiments. A tungsten filament next to the chip was used to load the helium surface with electrons in what you might consider the equivalent of a storage pool.
