If neutrinos carry non-zero electric charge, they would interact directly
with photons. This would induce a phase shift along the photon path in the
optical experiment. We propose a novel idea to detect this phase shift induced
by cosmic neutrino background (CNB) and the photon interaction using laser
interferometry experiment. We show that our setup can probe the CNB neutrino
charge in the order of 10β18eβ10β17e. This is quite competitive
with the existing upper bound on neutrino charge from both laboratory
experiments and astrophysical observations.Comment: 10 pages, 4 figure