A variety of technologies are currently in the spotlight as frontrunners for creating viable quantum computers. Companies have successfully constructed machines featuring dozens to hundreds of qubits, witnessing a decline in error rates, and have shifted their focus from theoretical challenges to practical engineering issues.
Despite the advanced stage of development in the field, some firms continue to explore new qubit technologies, convinced they can achieve scalability that positions them favorably in the competitive landscape. Recently, EeroQ, one of these companies, released a paper detailing the physics behind its innovative qubit system, which utilizes isolated electrons suspended above a layer of liquid helium.
Trapping single electrons
How does one manage to suspend an electron above liquid helium? To clarify this process, Ars reached out to Johannes Pollanen, chief scientific officer at EeroQ. He explained that the underlying principles of this phenomenon are well-established, with initial demonstrations occurring nearly fifty years ago.
“When a charged particle such as an electron approaches the surface of helium, it generates a small image charge beneath the liquid due to helium’s dielectric properties,” Pollanen noted. “This creates a weak positive charge that attracts the electron. However, the electron is unable to reach this positive charge because helium is chemically inert, leaving no spaces available for electrons to traverse.”
Achieving and maintaining liquid helium requires extremely low temperatures, yet it can remain in liquid form up to 4 Kelvin. This is advantageous as it eliminates the need for the highly advanced refrigeration systems necessary for other technologies like transmons. Furthermore, such low temperatures naturally create a vacuum, as most other substances will condense onto the walls of the containment vessel.
