  Motivated to measure the QED birefringence and to detect pseudoscalar-photon
interaction, we started to build up the Q & A experiment (QED [Quantum
Electrodynamics] and Axion experiment) in 1994. In this talk, we first review
our 3.5 m Fabry-Perot interferometer together with our results of measuring
Cotton-Mouton effects of gases. We are uprading our interferometer to 7 m
armlength with a new 1.8 m 2.3 T permanent magnet capable of rotation up to 13
cycles per second. We will use 532 nm Nd:YAG laser as light source with cavity
finesse around 100,000, and aim at 10 nrad/Hz^{1/2} optical sensitivity. With
all these achieved and the upgrading of vacuum, QED birefringence would be
measured to 28% in about 50 days. Along the way, we should be able to improve
on the dichroism detection significantly.
