Interplay between phonon downconversion efficiency, density of states at Fermi energy, and intrinsic energy resolution for microwave kinectic inductance detectors

Understand

Microwave Kinetic Inductance detectors (MKIDs) have been recognized as a powerful new tool for single photon detection.

• These highly multiplexed superconducting devices give timing and energy measurement for every detected photon.
• However, the full potential of MKID single photon spectroscopy has not been reached , the achieved energy resolution is lower than expected from first principles.
• Here, we study the efficiency in the phonon downconversion process following the absorption of energetic photons in MKIDs.