Physicists at the University of Basel in Switzerland have succeeded in cooling a nanoelectronic chip to a temperature lower than 3 mK. The research team, led by Basel physicist Professor Dominik Zumbühl, used magnetic cooling to cool the electrical connections as well as the chip itself. The results were published in the journal Applied Physics Letters.

With magnetic cooling, researchers can cool a system down when an applied magnetic field is ramped down while any external heat flow is avoided. Before ramping down, however, researchers must remove the heat of magnetization with another method to obtain efficient magnetic cooling.

Zumbühl’s group first cooled all of the chip’s electrical connections to 150 mK, a temperature less than a thousandth of a degree away from absolute zero, and then integrated a second cooling system directly into the chip itself to bring the system down to 2.8 mK. The temperature was maintained for a period of seven hours. “The combination of cooling systems allowed us to cool our chip down to below 3 mK, and we are optimistic that we can use the same method to reach the magic 1 mK limit,” says Zumbühl.