Single Quantum Dot as an Optical Thermometer for Millikelvin Temperatures

A single self-assembled quantum dot, with its atom-like electrical and optical properties, is an ideal probe of the rich physics of natural fermionic systems. An important prerequisite for many experiments is the precise knowledge of the temperature of an electron reservoir. By optically probing a Zeeman-split electronic state of a quantum dot coupled to a thermal electron reservoir, the temperature of this reservoir can be measured down to the millikelvin range.