UNSW touts 'hot qubits' as breaking practical quantum computing constraints

Researchers have published a proof of concept they say promises warmer, cheaper, and more robust quantum computing.

A team of researchers from the University of New South Wales (UNSW) have published a proof of concept that they say can deliver warmer, cheaper, and more robust quantum computing.

According to UNSW, it can be manufactured using conventional silicon chip foundries.

"Most quantum computers being developed around the world will only work at fractions of a degree above absolute zero. That requires multi-million-dollar refrigeration and as soon as you plug them into conventional electronic circuits they'll instantly overheat," the university explained.

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According to UNSW Professor Andrew Dzurak, the researchers' findings address this problem, saying the new results have opened a path from experimental devices to affordable quantum computers for real-world business and government applications.

The university touts that the proof-of-concept quantum processor unit cell, on a silicon chip, works at 1.5 Kelvin, which is 15 times warmer than the main competing chip-based technology being developed by Google, IBM, and others, which uses superconducting quantum bits (qubits).

"This is still very cold, but is a temperature that can be achieved using just a few thousand dollars' worth of refrigeration, rather than the millions of dollars needed to cool chips to 0.1 Kelvin," Dzurak explained. "While difficult to appreciate using our everyday concepts of temperature, this increase is extreme in the quantum world."

The UNSW researchers believe they have overcome one of the hardest obstacles standing in the way of quantum computers becoming a reality, with the proof-of-concept quantum processor unit cell not needing to operate at temperatures below one-tenth of one Kelvin.

In explaining the research, UNSW said qubit pairs are the fundamental units of quantum computing, and like its classical computing analogue -- the bit -- each qubit characterises two states, a 0 or a 1.

"Unlike a bit, however, it can manifest both states simultaneously, in what is known as a 'superposition'," the university said.

UNSW said the unit cell developed by Dzurak's team comprises two qubits confined in a pair of quantum dots embedded in silicon. The result, scaled up, can be manufactured by using existing silicon chip factories and would operate without the need for multi-million-dollar cooling, it added.

"It would also be easier to integrate with conventional silicon chips, which will be needed to control the quantum processor," UNSW continued, noting that a quantum computer that is able to perform the complex calculations would require millions of qubit pairs, and is generally accepted to be at least a decade away.

"Every qubit pair added to the system increases the total heat generated," Dzurak added. "And added heat leads to errors. That's primarily why current designs need to be kept so close to absolute zero."

The research was published by Dzurak's team, alongside researchers in Canada, Finland, and Japan, in a paper published in the journal Nature.