Students Shalom,

I remind the assignment

A "bomb" always explodes if a single photon reaches its vicinity. 
Sometimes the bomb is placed in a particular place. You have to use the 
MZI to find the bomb without exploding. The scheme needs not to be 100% 
efficient. Sometimes you do explode the bomb. But sometimes you can deduce 
with certainty that the bomb is in the place and it is still intact.

Lev