“…Therefore, the purity is of course bounded, i.e., The above relation ( 18 ) shows that for small the hyperbolic tangent above approaches . From Equation ( 18 ), we can isolate the variable in the fashion Now, introducing Equation ( 20 ) into Equation ( 15 ), we find the entropy S can be cast as a function of just D [ 17 ]. Thus, we reach the wished-for possibility of expressing the entropy solely in terms of the purity We clearly see that maximum D yields zero entropy, and the third law of thermodynamics can be applied in terms of purity.…”