Semiclassical Broadening in Quantum Dot Thermometry

Abstract

We studied the experimental conditions required for the accurate measurement of the electron temperature by using quantum dot (QD) thermometry. The physical requirements were examined by numerically evaluating the QD conductance as a function of QD-reservoir coupling and the electron temperature. An empirical formula for the Coulomb blockade peak at all coupling strengths was suggested. Thereafter, practical limitations set by voltage noise were investigated through a semiclassical treatment of the QD. A noise-broadening, in addition to thermal broadening, was identified, and a noise limit was provided for a given electron temperature. The analysis was applied to a realistic measurement setup by considering a dilution fridge equipped with low-pass RC-filters. We found that careful placements of filters were crucial in order to avoid thermal noise from the filters while measuring ultralow electron temperatures.