Microchip cooled to lowest-ever temperature, barely above absolute zero

Scientists have managed to cool a nanoelectronic chip to just 3 millikelvin, the coldest temperature ever achieved and just a fraction of a centigrade above absolute zero.

Physicists at the University of Basel in Switzerland used magnetic cooling to cool the electrical connections as well as the chip itself (pictured above).

By cooling equipment to as close to absolute zero as possible, unique experiments can be carried out as the temperature creates the ideal conditions for research into quantum computing and allows for entirely new physical phenomena to be examined.

Absolute zero is 0 kelvin or -273.15°C, 3 millikelvin is equivalent to just -273.147.

Magnetic cooling is based on the fact that a system can cool down when an applied magnetic field is ramped down while any external heat flow is avoided.

Before ramping down, the heat of magnetisation needs to be removed with another method to obtain efficient magnetic cooling.

Basel physicist Professor Dominik Zumbühl and his team succeeded in cooling a nanoelectronic chip to a temperature below 2.8 millikelvin, achieving a new low temperature record.

Dr Mario Palma, lead author of the study, and his colleague Christian Scheller successfully used a combination of two cooling systems, both of which were based on magnetic cooling. They cooled all of the chip’s electrical connections to temperatures of 150 microkelvin - a temperature that is less than a thousandth of a degree away from absolute zero.

They then integrated a second cooling system directly into the chip itself, and also placed a Coulomb blockade thermometer on it.

The construction and the material composition enabled them to magnetically cool this thermometer to a temperature almost as low as absolute zero as well.

“The combination of cooling systems allowed us to cool our chip down to below 3 millikelvin and we are optimistic than we can use the same method to reach the magic 1 millikelvin limit,” Zumbühl said.

The scientists managed to maintain these extremely low temperatures for a period of seven hours, providing enough time to conduct various experiments that will help to understand the properties of physics close to absolute zero.

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