Main Question or Discussion Point
When a particle is observed, an interaction must happen between it and the measuring apparatus. But, this interaction mostly (if not always) leads to the loss of the particle, and hence, can't be used again to do the same experiment or different experiments. I know that particles are identical (photons are identical to each other, electrons are identical to each other, and so on), but is it possible to conserve the particle & prevent losing it? or is it an inevitable loss for the sake of measurement? Will we get interesting results if this was possible? or is it useless?