A groundbreaking quantum device utilizing giant rubidium atoms may redefine temperature measurement.

While some nations utilize Celsius or Fahrenheit to measure temperature, physicists universally rely on Kelvin. This unit signifies “absolute temperature,” where 0 Kelvin represents the lowest temperature permitted by physical laws. However, confirming the accuracy of a 1 Kelvin measurement is a meticulous endeavor.

“When making absolute temperature measurements, one typically purchases a temperature sensor calibrated against another sensor, and the chain continues. Ultimately, one of those sensors was previously sent to the American Standards Institute,” explains Noah Schlossberger from NIST in Colorado.

Schlossberger and his team have developed an innovative device leveraging quantum mechanics to directly measure Kelvin, eliminating the need for extensive sensor calibrations.

This device, a compact metal and glass structure housing trapped rubidium atoms, employs lasers to displace outer electrons far from the atomic nucleus, resulting in significantly enlarged atoms. Subsequently, the researchers cool these atoms to roughly 0.5 milliKelvin—about 600,000 times cooler than room temperature—using lasers and electromagnetic fields.

Consequently, the outer electrons of rubidium atoms exhibit heightened sensitivity to minute temperature fluctuations. When exposed to certain quantum states, these electrons “jump,” allowing the device to function effectively as a temperature sensor. Established mathematical models can accurately relate the temperature difference necessary for such jumps, facilitating a new Kelvin definition.

The International Bureau of Weights and Measures similarly defines Kelvin via various quantum constants. Yet, institutions like NIST often resort to non-quantum devices for calibration. The new quantum device aims to deliver a calibration-free definition of Kelvin.

According to Schlossberger, “Every rubidium atom behaves identically in the same conditions. You can replicate a device anywhere in the world, and it will perform the same way.” This uniformity is crucial for maintaining high-precision instruments, such as atomic clocks, which require operation at very low Kelvin temperatures.

However, the prototype still faces challenges: it struggles with accurately detecting quantum states and is currently too cumbersome for practical use. Researchers are actively refining the design for enhanced practicality and precision.

Schlossberger presented this groundbreaking research at the American Physical Society Global Physics Summit in Colorado on March 16th.