High resolution on-chip thermometry using a microstrip-coupled transition edge sensor

Our recent work demonstrated highly efficient coupling of broadband thermal photon radiation between the termination resistors of a superconducting microstrip transmission line measured using a transition edge sensor (TES). A simple modification of this scheme is presented that permits rapid thermometry of micron-scale objects at temperatures below 3 K. Broadband photon noise gives a limiting temperature sensitivity of 3.8 μK for a 1 s integration time for measurements at 0.5 K. In practice, phonon noise in the thermal link between the TES and the heat bath limits the achievable temperature resolution to about 30 μK for a typical TES with noise equivalent power of 2×10−17 W/Hz with the same integration time.