Quantum magnomechanical thermometry

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The measurement of temperature is fundamental to many aspects of science. There are two types of thermometers, so-called "primary" and "secondary" thermometers. Primary thermometers are based on fundamental physics that can be reproduced in any lab outfitted with the right equipment. Secondary thermometers, on the other hand, must be calibrated against a primary thermometer and can change depending on how they are measured. It is clearly advantageous to use primary thermometers, but in practice they are almost never used because they are expensive and difficult to implement. A simple, inexpensive primary thermometer would be a valuable addition to the market. With the growing importance of quantum technologies, which necessarily operate at extremely low temperatures, the demand for thermometers for use at cryogenic temperatures is growing. And while cryogenic refrigeration technologies are advancing, these thermometers are not. In fact, secondary thermometers for low temperatures are getting more expensive, as companies recognize that the growing demand means they can charge higher prices for calibrated secondary thermometers. Therefore, a market exists for useful primary thermometers at low temperatures (< 1 K). In this project, we will research a type of primary thermometer for low temperatures based on the thermal noise of a mechanical object, self-calibrating based on quantum shot noise. In particular, this will be based on a microwave measurement of mechanics, making it well suited to the cryogenic environment. This will build upon foundational work including a theoretical proposal for this thermometer (Magnon-Phonon Quantum Correlation Thermometry, C.A. Potts... J.P. Davis, Phys Rev Applied 13, 064001 2020) and our recent observations of mechanics in this system (Dynamical Backaction Magnomechanics, C.A. Potts... J.P. Davis, Phys Rev X 11, 031053 2021).