I am trying to find a consistent, non-circular definition of information, which includes quantum information. The two main definitions that recur are the von Neumann entropy and the superposition definition. Let's take the latter; the former is similar. This would mean that any change in the probability amplitudes would allow us to talk of a change of information. But following this definition, two simultaneous changes of information in two particles, with the corresponding probabilities of one particle being taken over by the probabilities of another particle, would seem like an exchange of information -- until one thinks about two entangled states changing their states without information being exchanged, or two different quantum states which cannot be distinguished via measurement. So somewhere in a definition of information should come a provision that a measurement must be able to distinguish between the two choices (without using some circular clause such as a condition that information is exchanged to call it a measurement). But that brings us back to the classic definition of information, which then eliminates the possibility of talking about an exchange of information in, for example, decoherence theories. So do we have to have two definitions: information (0/1) and quantum information (superposition)? All in all, I am confused. Can anyone give me a clear definition of information (which includes quantum information)? Thank you.