New technology, News, Quantum mechanics, Subatomic particles

Artificial atoms for quantum computers

Engineers from University of New South Wales (UNSW), in Kensington, Australia, created artificial atoms in silicon chips to increase stability in quantum computers.

Source: Phys.org

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.

Quantum dots and qubits are explained in the post about the first part of Quantum Computing.

Quantum Computing (Part 1)Click here

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.

“The idea of creating artificial atoms using electrons is not new, in fact it was first proposed theoretically in the 1930s and then experimentally demonstrated in the 1990s—although not in silicon. We first made a rudimentary version of it in silicon back in 2013,” says Professor Dzurak, who is an ARC Laureate Fellow and is also director of the Australian National Fabrication Facility at UNSW, where the quantum dot device was manufactured.

Professor Dzurak and his team from UNSW’s School of Electrical Engineering—including Ph.D. student Ross Leon who is also lead author in the research, and Dr. Andre Saraiva—configured a quantum device in silicon to test the stability of electrons in artificial atoms.

They applied a voltage to the silicon via a metal surface ‘gate’ electrode to attract spare electrons from the silicon to form the quantum dot, an infinitesimally small space of only around 10 nanometres in diameter.

“As we slowly increased the voltage, we would draw in new electrons, one after another, to form an artificial atom in our quantum dot,” says Dr. Saraiva, who led the theoretical analysis of the results.

“In a real atom, you have a positive charge in the middle, being the nucleus, and then the negatively charged electrons are held around it in three dimensional orbits. In our case, rather than the positive nucleus, the positive charge comes from the gate electrode which is separated from the silicon by an insulating barrier of silicon oxide, and then the electrons are suspended underneath it, each orbiting around the centre of the quantum dot. But rather than forming a sphere, they are arranged flat, in a disc.”

These figures were taken from the article in Nature Communications, whose link is found here.

Quantum dot is in G1 gate and it’s indicated by the red sphere. RES transmit electrons. CB serves as confinement. The cobalt structure acts like a magnet. This image uses false colors.
Device’s cross-sectional schematics.

 

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