Physicists build quantum refrigerator based on four quantum dots: The proposed system consists of four quantum arranged in a square configuration, which the researchers call a "quadridot." The scientists theoretically showed that this quadridot acts as a quantum refrigerator when coupled to four independent reservoirs (one hot, one cold, and two of intermediate temperature). The quadridot pumps energy in the form of electrons from the hot reservoir and the cold reservoir to the intermediate-temperature reservoirs. When properly tuned, the quadridot can cool the quantum dot in contact with the cold reservoir to a temperature that is lower than its original temperature.
This configuration overcomes one of the biggest difficulties in realizing self-contained quantum refrigerators, which is engineering the interaction among the hot-, cold-, and intermediate-temperature reservoirs. The quantum dot array provides a relatively simple way to achieve this three-body interaction that may be possible to experimentally realize in the future.