Millicharged dark matter detection with Mach-Zehnder interferometer

If the dark sector exists and communicates with Standard Model through $U(1)$ mixing, it is possible that electromagnetism would have influence on matter fields in sector, so-called millicharge particles (mCPs). Furthermore, highest mCPs could be particles. Recently has been shown slowed down captured by earth. As a result, number density of accumulated underground enhanced several orders magnitude as compared to our solar system. In this study, we propose use Mach-Zehnder (MZ) laser interferometer detect earth bound detection phase shifts photons. We show that, for mass lager than $1$ GeV, sensitivity probing mixing parameter $\epsilon$ reach low $10^{-11}$ if larger $1~\rm{cm^{-3}}$.