Some grad students at my university are studying the use of atom interferometers as a so-called "gravimeter" to look for nuclear contraband (uranium has high de

Some grad students at my university are studying the use of atom interferometers as a so-called "gravimeter" to look for nuclear contraband (uranium has high density, you may have heard) inside shipping containers. It was surprising to me to hear that this was in the realms of possibility. They can essentially do a 3D scan of the container showing the density within (With pretty poor resolution). With enough precise enough clocks, I imagine it might be possible to do the same by measuring timing differences. Funny thought, really.