Recent progress on the next generation double beta decay experiment with low-temperature macro-calorimeters (CUPID)

The Cuore Upgrade with Particle IDentification, or CUPID, is a proposed next generation double-beta decay experiment that requires a low-threshold optical photon light detector. The use of a secondary bolometer as a light detector is being investigated since, $\alpha$-particles (the main background of CUORE-0) could be tagged by comparing the heat and light signals for each event, given that the two betas from a neutrinoless double beta event would produce both heat and light (Cherenkov light in the case of TeO$_2$) while $\alpha$ events would produce only heat in the absorber. A baseline resolution of at least 20~eV is required in order to achieve a rejection factor of 99.9\% of the $\alpha$ background. I will review latest progress on CUPID, particularly the development of low-Tc superconducting Transition Edge Sensor technology.