Definition
Given a quantum system with two subsystems A and B, the term joint quantum entropy simply refers to the von Neumann entropy of the combined system. This is to distinguish from the entropy of the subsystems. In symbols, if the combined system is in state ,
the joint quantum entropy is then
Each subsystem has it own entropy. The state of the subsystems are given by the partial trace operation.
Read more about this topic: Joint Quantum Entropy
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