Probabilistic exact cloning and probabilistic no-signalling
Arun Kumar Pati · 1999
We show that non-local resources cannot be used for probabilistic signalling even if one can produce exact clones with the help of a probabilistic quantum cloning machine (PQCM). We show that PQCM cannot help to distinguish two statistical mixtures at a remote location. Thus quantum theory rules out the possibility of sending superluminal signals not only deterministically but also probabilistically. We give a bound on the success probability of producing multiple clones in an entangled system. All the useful information that can be transmitted has a universal speed limit, namely, the speed of light. In quantum mechanics the situation seems to be changed when Einstein, Podolsky and Rosen put forward their famous thought experiment on two systems that had interacted in the past but are no longer in direct contact [1]. These kind of systems are described by entangled states which show non-local correlations that cannot be explained by any local hidden variable theory [2]. In [1] they proved that the measurement outcome of one system can instantaneously affect the result of the other. This suggested that one can