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A quantum computer is a machine where qubits replace ordinary bits. A qubit can be not just a 0 or a 1, but both at the same time. One way to make a qubit is to take an electron and make it hover above the surface of liquid helium. The helium is cooled to below two degrees above absolute zero. On such a cold surface, the electron behaves like a float on water: it doesn't sink but stays on an invisible cushion.

To use such a float as a qubit, you need to be able to determine its state. To do this, the work employs resonators — devices that respond to a specific frequency, like a tuning fork to sound. The electron changes the resonator's response, and from this change you can tell the qubit's state. But at ultra-low temperatures, ordinary electronics are noisy and interfere with the measurement. So the author created a special microwave source that works right inside the refrigerator and adds almost no interference.

The second option is solid neon. This is frozen gas, also cooled to cryogenic temperatures. Electrons above neon can maintain their quantum state longer, which is important for computations. The developed readout methods work for both platforms.

Such qubits are not fast yet, but they are very stable. If we learn to control them without errors, we could build a quantum computer that doesn't overheat and isn't thrown off by random interference.

Original abstract

as written by the authors arXiv:2601.21313

In this dissertation, resonator-based readout techniques were developed for floating electrons as qubits on cryogenic substrates, using two platforms: electrons on liquid helium and electrons on solid neon. In addition, a cryogenic microwave source was developed to enable low-noise measurement for qubit readout.