Team at Okinawa Institute of Science and Technology (OIST) has discovered a new method, called image charge detection, to detect electrons’ transitions to quantum states.
Electron needs to be immobilized to be used as quantum bit. To create an electron-capturing system, the researchers used liquid helium as a substrate. Since helium is free of impurities, these electrons are expected to retain quantum states longer than in any other materials, which is important for realizing a quantum computer. They placed a parallel-plate capacitor inside of a copper cell cooled to 0.2 degrees Kelvin and filled with condensed liquid helium. Electrons generated by a tungsten filament sat atop the liquid helium’s surface, between the two capacitor plates. Then, microwave radiation introduced into the copper cell excited electrons’ quantum states, causing the electrons to move away from the bottom capacitor plate and come closer to the top capacitor plate.
The excitation of quantum states was confirmed by observing an electrostatic phenomenon called image charge. Like a reflection in a mirror, image charge precisely reflects the movement of electrons. If an electron moves further from the capacitor plate, then the image charge moves alongside it. (OIST)