Spooky action at a distance

Thus, any quantum system that can be localized would play the role of a measuring device or as a device able to be used and/or integrated with others in more involved circuitry. The concept of quantum states for quantum measurements may help developing a rational quantum-physical framework with no spooky action at a distance, etc. Extensions leading to... 

Quantum theory predicts and experiments confirm that when measurements are made on two particles that once interacted but now are separated by an unlimited distance the results obtained in the measurement on one particle depend on the results obtained from the measurement on the second particle and depend on which property of the second particle is measured. Such instantaneous spooky actions at a distance (Einstein s phrase) have led one physicist to remark that quantum mechanics is magic (D. Greenberger, quoted in N. D. Mermin, Physics Today, April 1985, p. 38). 

The idea of action at a distance was resisted both by Newton, and by Einstein [42] who called it "spooky", but it has now been demonstrated experimentally [43, 44] that local realistic theory cannot account for correlations between measurements performed at well separated sites. The conclusion is that quantum theory permits hidden variables and is non-local. This conclusion is at variance with relativity, but, as pointed out by Bohm [34], the nonlocality of quantum theory only applies to complex wave functions and does not imply that the quantum potential can be used to transmit signals faster than light. 

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