Interesting. Here's an idea. How about separating the entangled ions by a long distance. Then "tickle" an atom on one side creating an "on/off" activity that can be "seen" and measured in the ion at the other end. Measure that "on/off" and interpret them as 0's and 1's. Instant (read: faster than light) communication between two points in space. Seems like a more fun investigation than using it as a "optical gradiometer".