(BBC) ColdQuanta recently signed a contract with US defence research agency Darpa to build a quantum computer that can rapidly work out how best to reposition radar equipment in the event of a defence system partially failing. The project relies on being able to gather together enough atoms as qubits – the building blocks of a quantum computer, which allow it to perform calculations.
To do this, the atoms have to be extremely cold, making such computers the coldest in the world.
“What we’re asked to do over the next 40 months is be able to have a machine that has thousands of qubits to solve a real-world defence-related problem and the one that we’re working on is a version of this radar coverage problem,” explains Bo Ewald, chief executive of ColdQuanta, based in Colorado.
There are various types of quantum computer in development but the approach using ultra-cold neutral atoms as qubits is unusual – it’s different from the superconducting quantum computers being developed by big firms such as IBM and Google, or other projects that use charged atoms, also known as ions, instead.
The superconducting folks are running at millikelvin… we’re down to microkelvin,” he explains. Kelvin is a measurement of temperature. Zero kelvin, absolute zero (-273.15C) is the coldest anything could ever be.
And while millikelvin is cold, at 0.001 kelvin, ColdQuanta’s microkelvin atoms are much colder – at roughly 0.000001 kelvin. Both are significantly colder, indeed, than anywhere we know about in the natural universe.

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