Production and detection of axion-like particles by interferometry

We propose an interferometry experiment for the detection of axion-like particles (ALPs). As in ordinary photon-regeneration (light shining through a wall) experiments, a laser beam traverses a region permeated by a magnetic field, where photons are converted to ALPs via the Primakoff process, resulting in a slight power loss and phase shift. The beam is then combined with a reference beam that originates from the same source. The detection of a change in the output intensity would signal the presence of ALPs (or possibly other particles that couple to the photon in a similar way). Because only one stage of conversion is needed, the signal is of O(gaγγ2), as opposed to O(gaγγ4) for photon-regeneration experiments, where gaγγ is the coupling between ALPs and photons. This improvement over photon-regeneration is nullified by the presence of shot noise, which however can be reduced by the use of squeezed light, resulting in an improvement in the sensitivity to gaγγ over ordinary photon-regeneration experiments by an order of 101/2 assuming 10 dB noise suppression. Additionally, our setup can incorporate straightforwardly optical delay lines or Fabry-Perot cavities, boosting the signal by a factor of n∼103, where n is the number of times the laser beam is folded. This way, we can constrain gaγγ better by yet another factor of n1/2∼101.5, as compared to the n1/4 boost that would be achieved in photon-regeneration experiments.