Innovation

The Quantum Refrigerator

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a solid-state refrigerator that uses quantum physics in micro- and nanostructures to cool a much larger object to extremely low temperatures. The refrigerator, which measures a few inches in outer dimensions, enables researchers to place any suitable object in the cooling zone and later remove and replace it.

The technology may offer a compact, convenient means of chilling advanced sensors below standard cryogenic temperatures—300 milliKelvin (mK), typically achieved by use of liquid helium—to enhance their performance in quantum information systems, telescope cameras, and searches for mysterious dark matter and dark energy.

The NIST refrigerator’s cooling elements, consisting of 48 tiny sandwiches of specific materials, chilled a plate of copper, 2.5 centimeters on a side and 3 millimeters thick, from 290 mK to 256 mK. The cooling process took about 18 hours. NIST researchers expect that minor improvements will enable faster and further cooling to about 100 mK.

The cooling elements are sandwiches of a normal metal. The temperature in the normal metal drops dramatically and drains electronic and vibrational energy from the object being cooled.

NIST researchers previously demonstrated this basic cooling method but are now able to cool larger objects that can be easily attached and removed. Researchers developed a micromachining process to attach the cooling elements to the copper plate, which is designed to be a stage on which other objects can be attached and cooled. Additional advances include better thermal isolation of the stage, which is suspended by strong, cold-tolerant cords.

Cooling to temperatures below 300 mK currently requires complex, large and costly apparatus. Researchers plan to boost the cooling power of the prototype refrigerator by adding more and higher-efficiency superconducting junctions and building a more rigid support structure.