Description
Vacuum magnetic birefringence (VMB) is a currently undetected con- sequence of quantum electrodynamics (QED) which results from the pre- diction of virtual electron-positron pairs allowing for the polarization of vacuum under the influence of a strong magnetic field. The ALPSII string consists of a 212m, 5.3T magnet string with modulation capabilities cur- rently in the mHz regime, which can produce a strong VMB signal. We propose a sensing scheme which measures the relative frequency changes between orthogonal laser fields frequency stabilized to a single optical cavity. The frequency drifts, which are proportional to the induced bire- fringence from VMB, are sensed with a local oscillator allowing for a heterodyne readout. With a goal of reaching sensitivities on the order of 10−17m√Hz in differential optical path length displacement, we present the ongoing work and initial results for the current prototype experiment, alongside a summary of the ALPSII infrastructure and its ability to measure birefringence on the QED level with the proposed scheme.
