That looks more like a description of what they are trying to do, not whats been done.
But tell me, are they using interferometers to detect gravity? (ie, using the affects of gravity on photons)
From what you posted, it looks like they are.
Well, a number of gravity wave detectors have already been built. LISA (Laser Interferometer Space Antenna) will be the first dedicated space-based gravitational wave detector, due to be launched around 2019 or so.
But tell me, are they using interferometers to detect gravity? (ie, using the affects of gravity on photons)
From what you posted, it looks like they are.
As I understand it, the lasers are used to measure the distance between a number of separated masses. As a gravitational wave passes by, it will induce motion in them. Even with "arms" 4 kilometers long, the strongest gravitational waves will only change the distance between the ends of the arms by at most roughly 10 to the minus 18th meters...so the lasers have to be really accurate!