By Josh Perry, Editor
[email protected]

Scientists at the University of Exeter (U.K.) have created a novel theoretical framework to characterize nanoscale thermometers and determine the ultimate achievable accuracy, which is impacted by fluctuation arising from quantum effects.

A new theoretical framework explains how quantum fluctuation impact nanoscale temperature measurement. (Advanced Thermal Solutions, Inc.)

According to a report from the university, “Tiny thermometers can be in a superposition between different temperatures, e.g. 90.5°C and 89.5°C, just like Schrödinger's cat can be in a superposition between being dead and alive.”

Temperature fluctuations are common even in standard thermometers because of the constant movement of mercury atoms. The reading could be 90°C but give or take 0.5°C because of the microscopic collisions.

Thermal noise occurs at the nanoscale as well, but researchers indicated the presence of quantum fluctuations that influence readings at that level.

“The discovery establishes a new connection between quantum uncertainty, arising from such superposition states, and the accuracy of temperature measurements,” the report continued. “In the future this uncertainty relation will be useful for experimentalists to design optimal nanoscale thermometers that take into account the effects of quantum mechanics.”

The research was recently published in Nature Communications. The abstract read:

“It is known that temperature estimates of macroscopic systems in equilibrium are most precise when their energy fluctuations are large. However, for nanoscale systems deviations from standard thermodynamics arise due to their interactions with the environment.

“Here we include such interactions and, using quantum estimation theory, derive a generalized thermodynamic uncertainty relation valid for classical and quantum systems at all coupling strengths. We show that the non-commutativity between the system’s state and its effective energy operator gives rise to quantum fluctuations that increase the temperature uncertainty.

“Surprisingly, these additional fluctuations are described by the average Wigner-Yanase-Dyson skew information. We demonstrate that the temperature’s signal-to-noise ratio is constrained by the heat capacity plus a dissipative term arising from the non-negligible interactions.

“These findings shed light on the interplay between classical and non-classical fluctuations in quantum thermodynamics and will inform the design of optimal nanoscale thermometers.”