ALP (axion like particle) is one of the best candidates for dark matter.
ALP dark matter oscillates around its small mass potential, and may be coupled to photons.
The axion-photon coupling causes the rotation of the linear polarization plane of a traveling photon, and several techniques exploiting this “axion-birefringence” have been developed to search for ALP dark matter.
Moreover, in a smaller mass region, ALP can play a role of dark energy (i.e. quintessence). CMB observation is sensitive to ALP dark energy coupled to photons which causes the isotropic conversion of E-mode polarization into B-mode, known as “cosmic birefringence”.
In this talk, I introduce the new techniques to search for ALP dark matter and discuss the sensitivity of the upcoming CMB experiment to ALP dark energy.