Quantum technology: prospects for new thermometric and radiometric sensor development

In the perspective, some new methods for measuring thermodynamic (or primary) temperature that exploit quantum effects are discussed. The techniques discussed are at various stages of development, so for each, the principles of operation, current and anticipated challenges and current status and progress are presented. First, the development of a thermometer based on cavity magnomechanics for cryogenic applications is discussed. This technique links temperature to a signal derived from the phonon modes in a magnetic element coupled to a microwave cavity. Second, progress in Coulomb blockade thermometry is discussed. Advances in the manipulation of atoms using scanning probe microscopy (SPM) have led to the creation of structures, such as single-electron transistors (SETs), with physical dimensions smaller than can be achieved using traditional lithography. A Coulomb blockade thermometer (CBT) fabricated at such small scales could operate at higher temperatures than previously demonstrated. Third, Rydberg thermal radiometry is discussed. The excited states of Rydberg atoms possess large dipole moments and interact strongly with blackbody radiation (BBR). Rydberg radiometry leverages these interactions to infer a source's temperature from the effect of its emitted BBR upon the quantum dynamics of Rydberg states. Fourth, thermometry via temperature-dependent optical emission from nanoparticles is discussed, which is expected to be particularly useful for biological applications; in addition, efforts are underway to achieve primary thermometry by this mechanism. This article is part of the Theo Murphy meeting issue 'The redefined kelvin: progress and prospects'.