Chapter 1: Introduction to Quantum Computing

Quantum computing faces a significant challenge: achieving stability. Environmental factors can easily disrupt quantum states, leading to a dramatic loss of information. To develop practical quantum computers and networks, researchers must ensure both stability and effective electron control.

In a recent study published in Nature Communications, engineers from UNSW Sydney unveiled their work on artificial atoms created within silicon 'quantum dots.' These innovations promise enhanced stability. In these minute structures, electrons serve as qubits—the fundamental units of quantum information. Unlike classical bits, which can only represent a '0' or '1', qubits can exist in a superposition of both states, exponentially increasing computational capacity.

This principle is famously illustrated by the Schrödinger’s Cat thought experiment, where the cat exists in a superposition of being both alive and dead, allowing for numerous calculations to be performed at once.

“This remarkable capability stems from the phenomenon of superposition,” explains the researchers at IBM.

Chapter 2: The Role of Electrons in Artificial Atoms

The electrons in an artificial atom orbit around a central area much like traditional atoms, though they lack a nucleus. “Creating artificial atoms using electrons is not a new concept; it was theoretically suggested in the 1930s and experimentally demonstrated in the 1990s, though not in silicon,” states Professor Dzurak, an ARC Laureate Fellow and director of the Australian National Fabrication Facility at UNSW. “We first developed a basic version in silicon in 2013, but our latest research shows that artificial atoms with a greater number of electrons are more robust qubits than previously thought.”

More electrons contribute to a more dependable process for quantum calculations. “This is crucial because qubits reliant on a single electron can often be unstable,” Dzurak adds.

Section 2.1: Constructing a Qubit Periodic Table

To optimize the arrangement of electrons for quantum computing and information storage, Dzurak and his team have devised a rudimentary 'periodic table' for qubits. He explains, “Much like the traditional periodic table listing elements by their electron count, we find that our artificial atoms also exhibit organized and predictable electron shells.”

Chapter 3: Testing Stability in Quantum Dots

To assess the stability of electrons in artificial atoms, the researchers applied voltage through a metal surface 'gate' electrode, attracting additional electrons to form the quantum dot—an extremely small area measuring about 10 nm in diameter. “As we gradually increased the voltage, we drew in new electrons one by one to create an artificial atom,” explains Dr. Andre Saraiva, who led the theoretical analysis of the team's findings.

In traditional atoms, the positive charge is centralized in the nucleus, with electrons orbiting around it. In this case, the positive charge comes from the gate electrode, separated from the silicon by a silicon oxide barrier, causing the electrons to orbit in a flat disc shape rather than a spherical one.

Chapter 4: The Importance of Spin in Qubits

As Professor Dzurak elaborates, the key to utilizing electrons as qubits lies in controlling their quantum mechanical property known as spin. “An electron behaves like a tiny magnet, with its north pole pointing either up or down, representing a 1 or a 0, respectively. When electrons complete a shell, they align in opposite directions, resulting in a total spin of zero, rendering them ineffective as qubits. However, adding another electron initiates a new shell, giving us a usable spin for a qubit.”

The research indicates that the spin of valence electrons in artificial atoms can be effectively controlled, providing stable and reliable qubits for quantum information storage. The presence of multiple electrons enhances robustness.

“Our findings show that we can manipulate the spin of electrons in outer shells to yield stable qubits, which is crucial for developing less fragile qubits,” Dzurak emphasizes. “One electron is quite delicate, but an artificial atom with five or more electrons is far more resilient.”

The team intends to build on their findings by examining how chemical bonding rules—determined by the number of valence electrons—affect their artificial atoms. This understanding could facilitate the creation of artificial molecules, paving the way for multi-qubit logic gates, representing a significant advancement toward developing large-scale silicon-based quantum computers.

The first video titled "Artificial atoms create stable qubits for quantum computing" elaborates on how artificial atoms can enhance stability in quantum computing.

The second video titled "Artificial Atoms: The Quantum Around You. Ep 8" explores the implications of artificial atoms in quantum technology.