  Pure state of a physical system can be prepared in an infinite number of
ways. Here, we prove that given a pure state of a quantum system it is
impossible to distinguish two preparation procedures. Further, we show that if
we can distinguish two preparation procedures for the same pure state then that
can lead to signalling. This impossibility result is different than the no
measurement without disturbance and the no-cloning. Extending this result for a
pure bipartite entangled state entails that the impossibility of distinguishing
two preparation procedures for a mixed state follows from the impossibility of
distinguishing two preparations for a pure bipartite state.
