Laboratory setup for using giant "Rydberg" atoms to measure temperature. The glowing red orb shows the cloud of approximately one million rubidium atoms used in the setup.
N. Schlossberger/NIST
Scientists at the National Institute of Standards and Technology (NIST) have created a new thermometer using atoms boosted to such high energy levels that they are a thousand times larger than normal. By monitoring how these giant "Rydberg" atoms interact with heat in their environment, researchers can measure temperature with remarkable accuracy. The thermometer's sensitivity could improve temperature measurements in fields ranging from quantum research to industrial manufacturing.
Unlike traditional thermometers, a Rydberg thermometer doesn't need to be first adjusted or calibrated at the factory because it relies inherently on the basic principles of quantum physics. These fundamental quantum principles yield precise measurements that are also directly traceable to international standards.
"We're essentially creating a thermometer that can provide accurate temperature readings without the usual calibrations that current thermometers require," said NIST postdoctoral researcher Noah Schlossberger.
Revolutionizing Temperature Measurement
The research, published in Physical Review Research, is the first successful temperature measurement using Rydberg atoms. To create this thermometer, researchers filled a vacuum chamber with a gas of rubidium atoms and used lasers and magnetic fields to trap and cool them to nearly absolute zero, around 0.5 millikelvin (thousandths of a degree). This means the atoms were essentially not moving. Using lasers, they then boosted the atoms' outermost electrons to very high orbits, making the atoms approximately 1,000 times larger than ordinary rubidium atoms.
In Rydberg atoms, the outermost electron is far away from the core of the atom, making it more responsive to electric fields and other influences. This includes blackbody radiation, the heat emitted by surrounding objects. Blackbody radiation can cause electrons in Rydberg atoms to jump to even higher orbits. Rising temperatures increase the amount of ambient blackbody radiation and the rate of this process. Thus, researchers can measure temperature by tracking these energy jumps over time.
R. Jacobson/NIST
This approach enabled the detection of even the most minor temperature changes. While there are other types of quantum thermometers, Rydberg thermometers can measure the temperature of their environment from about 0 to 100 degrees Celsius without needing to touch the object being measured.
This breakthrough not only paves the way for a new class of thermometers but is particularly significant for atomic clocks, because blackbody radiation can reduce their accuracy.
"Atomic clocks are exceptionally sensitive to temperature changes, which can cause small errors in their measurements," said NIST research scientist Chris Holloway. "We're hopeful this new technology could help make our atomic clocks even more accurate."
Beyond precision science, the new thermometer could have wide-ranging applications in challenging environments from spacecraft to advanced manufacturing plants, where sensitive temperature readings are essential.
With this development, NIST continues to push the boundaries of science and technology.
"This method opens a door to a world where temperature measurements are as reliable as the fundamental constants of nature," Holloway added. "It's an exciting step forward for quantum sensing technology."
Paper: Noah Schlossberger, et al. Primary quantum thermometry of mm-wave blackbody radiation via induced state transfer in Rydberg states of cold atoms. Physical Review Research. Published online Jan. 23, 2025. DOI: 10.1103/PhysRevResearch.7.L012020
