The liquid helium-free dilution refrigerator has successfully achieved extremely low temperature operation below 10mK (0.01 degrees above absolute zero)

It is reported that the liquid helium-free dilution refrigerator independently developed by the Institute of Physics, Chinese Academy of Sciences has successfully achieved low temperature operation below 10mK (0.01 degrees above absolute zero). This marks a breakthrough in the development of cryogenic instruments in my country.

The dilution refrigerator is a high-end scientific research instrument that can provide an environment close to absolute zero. It is widely used in scientific research fields such as condensed matter physics, material science, particle physics and even astronomical detection. The liquid helium-free dilution refrigerator is a commercially available low-temperature refrigerator. It can achieve a low temperature of only 0.01 degrees above absolute zero without the assistance of liquid helium, which can provide quantum computer chips with the necessary requirements for maintaining the quantum state. low temperature environment.

"Different from traditional wet dilution refrigerators that rely on liquid helium-assisted cooling, liquid helium-free dilution refrigerators do not require liquid helium supply, have large sample space, long continuous operation time, and are convenient for operation and maintenance. Mainstream," said Ji Zhongqing, an associate researcher at the Institute of Physics, Chinese Academy of Sciences.

Quantum computing is the main battlefield of scientific and technological competition among countries around the world. The dilution refrigerator provides the necessary lower temperature environment for the normal operation of quantum computers, and is an irreplaceable key device in quantum computing research. "At present, such instruments in my country are completely dependent on imports, which are the key core technologies that need to be broken. Therefore, it is imminent to develop a domestic liquid-free helium dilution refrigerator." Ji Zhongqing said frankly.

As the birthplace of low-temperature experimental technology and low-temperature physics research in China, the Institute of Physics, Chinese Academy of Sciences successfully developed my country's first wet dilution refrigerator as early as the late 1970s, achieving a temperature of 34mK (minus 273.116 degrees, that is, 0.034 degrees above absolute zero). ) at lower temperatures. Facing the new situation of a new round of quantum technology competition, the research team of the institute once again organized a joint effort to develop a domestic liquid helium-free dilution refrigerator.

"During the two-and-a-half-year research and development process, we overcame the problem of low-temperature equipment welding process, and solved the long-standing problems of cold leakage and excess leakage. In the production process of the core low-temperature and high-efficiency heat exchanger, a large number of materials were tested and evaluated. And a variety of design solutions, to overcome a number of core technical problems such as coil heat exchangers and silver powder heat exchangers." Ji Zhongqing said.

Finally, on the evening of June 24, 2021, the prototype of the liquid helium-free dilution refrigerator independently developed by the institute successfully achieved a continuous and stable operation of 10.9mK (minus 273.1391 degrees, that is, 0.0109 degrees above absolute zero), which meets the requirements of superconducting quantum computing. According to the required conditions, the single-stroke operation mode can be lower than 8.7mK (minus 273.1413 degrees, that is, 0.0087 degrees above absolute zero), which basically reaches the level of international mainstream products.

Ji Zhongqing said that the newly developed prototype of the liquid helium-free dilution refrigerator has taken a key step in solving the "stuck neck" problem of quantum computing and accelerating the self-reliance of science and technology. Cutting-edge research provides the ability to guarantee lower temperature conditions.

"In the future, the research team of the Institute of Physics will further optimize the related technologies of the liquid helium-free dilution refrigerator and the solidification process. The new generation of refrigerators under construction will reach the level of imported products in terms of ease of use and stability, and will provide a solid foundation for my country's quantum computing. Experimental frontier research provides strong support." Ji Zhongqing said.

Source: People's Daily