Cryogenic CMOS IC operates at -270ºC, controls up to 128 qubits
“There are many issues to be resolved before we have a working large-scale quantum computer,” said team lead Fabio Sebastiano from QuTech and the Faculty of Electrical Engineering, Mathematics and Computer Science. “The quantum information stored in qubits can rapidly degrade and become unusable unless qubits are cooled down to temperatures very close to absolute zero (-273 degrees Celsius, or 0 Kelvin). For this reason, qubits typically operate inside special refrigerators at temperatures as low as 0.01 K, controlled by conventional electronics working at room temperature.”
One wire is required to connect each qubit to the control electronics. While this is feasible for the small number of qubits now in operation, the approach will become impractical for the millions of qubits required in useful quantum computers.
in the cryogenic refrigerator. Credit QuTech.
“It would be equivalent to taking the 12-megapixel camera on your mobile phone and trying to individually wire each of the million pixels to a separate electronic circuit,” explained Sebastiano. “A more viable solution is to operate the electronics controlling the qubits at extremely low (cryogenic) temperatures, so they can be placed as close as possible to the qubits.”
QuTech teamed up with Intel to address this precise challenge. The result is called Horse Ridge – an integrated circuit named after one of the coldest spots in Oregon.
“We have designed and fabricated a CMOS integrated circuit able to control up to 128 qubits, which can operate at 3 K (-270 °C) and can therefore be described as a cryo-CMOS circuit”, said Sebastiano. This is the same technology employed for standard microprocessors and such cryo-CMOS circuits could be used to create large-scale quantum computers.
The researchers demonstrated experimentally both proper operation of the integrated circuit and an ability to drive a real spin qubit. The next challenge is to close the remaining temperature gap. “Spin qubits are expected to function at slightly higher temperatures than is achieved now, say above 1,5 K,” explains Sebastiano. “Our cryo-CMOS circuit now works at 3 K. If we can bridge this temperature gap, we could integrate both qubits and their controlling electronics into the same package or chip, thus achieving an extremely compact system.”
The work presented at ISSCC describes the Intel 22-nm FFL FinFET cryo-CMOS controller that operates at 3 K over the wide band from 2 to 20 GHz and is able to drive up to 128 frequency-multiplexed spin qubits or transmons in a 1GHz band.
QuTech – www.qutech.nl
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