A note on Bianchi-Donà's proof to the variance formula of von Neumann entropy
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Bianchi and Donà [1] have recently reported a proof to the variance formula of von Neumann entropy, which was conjectured in [2] and firstly proved in [3]. The purpose of this short note is to show that, despite having a different starting point, the subsequent calculations (omitted in [1]) leading to the result are essentially the same as in [3].
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