This bothers me a bit. Are the two diamonds not reacting as a single system just because the split laser beam reaches them at exactly the same time? The experiment seems to be saying more about the laser than the diamonds. What if one of the diamonds was moved a cm. further sway so the laser hit it slightly later? Would the synchronized behavior then break down? I believe that other entanglement experiments have separated the members or isolated one and still seen entanglement. But I'm not so sure this one is an authentic example of the phenomenon. Or maybe the article's description is over-simplified and my misgivings were accounted for in the experimental design.
They’re not looking at the phase relationship between the two pulses. They’re looking at the light’s frequency. Moving one of the diamonds would introduce a phase shift, but that wouldn’t explain the frequency shift.