Here you go. The paper below looks at whether you might in principle distinguish between many-worlds and single-world versions of QM by observation.
I'm not saying I agree with the content, but make the points that (a) this is an example of a scientist trying to find a way of testing the multiverse hypothesis experimentally and (b) you'll see in the conclusion that the speculative nature of the work is appropriately acknowledged.
http://xxx.lanl.gov/pdf/gr-qc/0001001v1.pdf