Quantum Erasure?

Hi, My question is about the famous "double slit experiment". I have read some variations about this experiment and just wanted to know if these variations are true. You get interference pattern when; 1-Detectors are on but not saving any data. 2-Detectors are on and saving but saved data deleted immediately.
- Ali (age 32)
Turkey

This is a subtle question. What determines whether the interference is lost is not whether the data are recorded in a form suitable for people to read. What matters is whether the detectors, or anything else, causes something somewhere to go into different states depending on which path was taken. If that happens, then the quantum states of the particles and that (possibly remote) something get "entangled" and the interference is lost, regardless of whether the which-path data is actually "recorded" anywhere. If there is no such entanglement between the path and some other system, then the interference persists.

A good search term to read further is "quantum erasure" -- it's possible to recover the interference by making a measurement on that other system, obscuring the original path of the particle; this amounts to selecting a portion of the events that display interference. 

Mike W. (with key help from Paul Kwiat)

(published on 02/18/2014)