Extending To The Multipartite Case
The above discussion generalizes easily to the case of a quantum system consisting of more than two subsystems. Let a system have n subsystems and have state space . A pure state is separable if it takes the form
Similarly, a mixed state ρ acting on H is separable if it is a convex sum
Or, in the infinite dimensional case, ρ is separable if it can be approximated in the trace norm by states of the above form.
Read more about this topic: Separable State
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