Researchers at Osaka University have achieved readout of spin-polarized many-electron states, consisting of three or four electrons. Writes about this Physical Review Letters.

The researchers improved upon previous methods that could easily resolve only two electrons using spin filtering caused by the quantum Hall effect. According to the authors of the scientific work, their achievement can lead to the creation of quantum computers based on multielectron high-spin states.

Scientists have shown how to read the spin state of many electrons trapped in a tiny quantum dot made from gallium and arsenic. Quantum dots act like artificial atoms with properties that scientists can tune by changing their size or composition. However, the gaps in the energy levels usually become smaller and more difficult to resolve as the number of captured electrons increases.

To overcome this, the team used a phenomenon called the quantum Hall effect. When electrons are confined to two dimensions and exposed to a strong magnetic field, their states are quantized, so their energy levels can only take on certain specific values.

“Previous spin measurement readout methods could only handle one or two electrons, but using the quantum Hall effect, we were able to resolve up to four spin-polarized electrons,” says lead author Haruki Kiyama.

To prevent disturbances from thermal vibrations, the experiments were carried out at extremely low temperatures, around 80 millikelvin. “This readout method could pave the way for faster and more powerful spin-based quantum information processing devices with multi-electron spin states,” adds senior study author Akira Oiwa.