Probing virtual axion-like particles by precision phase measurements

We propose an experiment for detecting Axion-Like Particles (ALPs) based on the axion-photon interaction in the presence of a non-uniform magnetic field. The impact of virtual ALPs on the polarization of the photons inside a cavity is studied and a detection scheme is proposed. We find that the cavity normal modes are dispersed differently owing to their coupling to the ALPs in the presence of a background magnetic field. This birefringence, in turn, can be observed as a phase difference between the cavity polarization modes. The signal is considerably enhanced for a squeezed light source. We argue that the amplified signal allows for exclusion of a range of axion mass 6 x 10(-4) eV less than or similar to m(a) less than or similar to 6 x 10(-3) eV even at very small axion-photon coupling constant with the potential to reach sensitivity to the QCD axion. Our scheme allows for the exclusion of a range of axion masses that has not yet been covered by other experimental techniques.