- In the last 20 years, many circuits have been realized where single electrons are trapped in small regions delimited by thin insulating barriers. Based on electron trapping, controlled transport of single electrons has been achieved, and spectroscopic measurements of quantum dots and molecules have been developed.
In our experiment, we show that single electrons can also be trapped without barriers. Our trap is an atomic-size contact between two superconductors with different macroscopic phases. Whereas most electrons are paired at the temperature of the experiment, we find that unpaired electrons tend to be trapped at the atomic contact and stay there for more than 100µs. The trapping of an electron is revealed by the suppression of the supercurrent that flows between the superconductors. The dynamics of trapping and untrapping displays surprising features yet to be understood.
While trapping single electrons in superconductors can be detrimental to the functioning of qubits and detectors, it could open the way to individual spin manipulation and to superconducting spin qubits.
