Hot qubits break one of the biggest constraints to practical quantum computers

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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.

But now researchers led by Professor Andrew Dzurak at UNSW Sydney have addressed this problem.

“Our new results open a path from experimental devices to affordable quantum computers for real world business and government applications,” says Professor Dzurak.

The researchers’ proof-of-concept quantum processor unit cell, on a silicon chip, works at 1.5 Kelvin—15 times warmer than the main competing chip-based technology being developed by Google, IBM, and others, which uses superconducting qubits.

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Inside the race to build the best quantum computer on Earth

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IBM thinks quantum supremacy is not the milestone we should care about.

Google’s most advanced computer isn’t at the company’s headquarters in Mountain View, California, nor anywhere in the febrile sprawl of Silicon Valley. It’s a few hours’ drive south in Santa Barbara, in a flat, soulless office park inhabited mostly by technology firms you’ve never heard of.

An open-plan office holds several dozen desks. There’s an indoor bicycle rack and designated “surfboard parking,” with boards resting on brackets that jut out from the wall. Wide double doors lead into a lab the size of a large classroom. There, amidst computer racks and jumbles of instrumentation, a handful of cylindrical vessels—each a little bigger than an oil drum—hang from vibration-damping rigs like enormous steel pupae.

On one of them, the outer vessel has been removed to expose a multi-tiered tangle of steel and brass innards known as “the chandelier.” It’s basically a supercharged refrigerator that gets colder with each layer down. At the bottom, kept in a vacuum a hair’s breadth above absolute zero, is what looks to the naked eye like an ordinary silicon chip. But rather than transistors, it’s etched with tiny superconducting circuits that, at these low temperatures, behave as if they were single atoms obeying the laws of quantum physics. Each one is a quantum bit, or qubit—the basic information–storage unit of a quantum computer.

Late last October, Google announced that one of those chips, called Sycamore, had become the first to demonstrate “quantum supremacy” by performing a task that would be practically impossible on a classical machine. With just 53 qubits, Sycamore had completed a calculation in a few minutes that, according to Google, would have taken the world’s most powerful existing supercomputer, Summit, 10,000 years. Google touted this as a major breakthrough, comparing it to the launch of Sputnik or the first flight by the Wright brothers—the threshold of a new era of machines that would make today’s mightiest computer look like an abacus.

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IBM makes 20 qubit quantum computing machine available as a cloud service

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IBM has been offering quantum computing as a cloud service since last year when it came out with a 5 qubit version of the advanced computers. Today, the company announced that it’s releasing 20-qubit quantum computers, quite a leap in just 18 months. A qubit is a single unit of quantum information.

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