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Arthur T Knackerbrackethas found the following story:

In a paper published today in Nature Communications, UNSW quantum computing researchers describe how they created artificial atoms in a silicon 'quantum dot', a tiny space in a quantum circuit where electrons are used as qubits (or quantum bits), the basic units of quantum information.

Scientia Professor Andrew Dzurak explains that unlike a real atom, an artificial atom has no nucleus, but it still has shells of electrons whizzing around the centre of the device, rather than around the atom's nucleus.

[...] [Ph.D. student Ross] Leon, who ran the experiments, says the researchers were interested in what happened when an extra electron began to populate a new outer shell. In the periodic table, the elements with just one electron in their outer shells include Hydrogen and the metals Lithium, Sodium and Potassium.

"When we create the equivalent of Hydrogen, Lithium and Sodium in the quantum dot, we are basically able to use that lone electron on the outer shell as a qubit," Ross says.

"Up until now, imperfections in silicon devices at the atomic level have disrupted the way qubits behave, leading to unreliable operation and errors. But it seems that the extra electrons in the inner shells act like a 'primer' on the imperfect surface of the quantum dot, smoothing things out and giving stability to the electron in the outer shell."

[...] It is the spin of an electron that we use to encode the value of the qubit, explains Professor Dzurak.

[...] "When the electrons in either a real atom, or our artificial atoms, form a complete shell, they align their poles in opposite directions so that the total spin of the system is zero, making them useless as a qubit. But when we add one more electron to start a new shell, this extra electron has a spin that we can now use as a qubit again.

"Our new work shows that we can control the spin of electrons in the outer shells of these artificial atoms to give us reliable and stable qubits.

Journal Reference:
Leon, R.C.C., Yang, C.H., Hwang, J.C.C. et al. "Coherent spin control of s-, p-, d- and f-electrons in a silicon quantum dot." Nat Commun 11, 797 (2020). DOI: 10.1038/s41467-019-14053-w

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