alt Hacker News> Entropy isn't a function of imperfect knowledge. It's a function of the possible states of a system and their probability distributions.
There are no probability distributions over possible states when there is perfect knowledge of the state.
> Quantum mechanics
Entropy is also zero for a pure quantum state. You won’t have entropy without imperfect knowledge.
Replies
mr_mitm • 06/16/2025
Just look at the definition of entropy. Knowledge about a system never enters the equation.
S := -k_B sum p_i ln (p_i)
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> There are no probability distributions over possible states when there is perfect knowledge of the state.
I know very little about physics but I thought that the leading interpretations of quantum physics say that the probability distribution is all we can know about a system. The entropy is not due to due to a lack of information about the quantum state, but because the outcomes are inherently stochastic?