 Infinitesimal unitary transformation (source code)

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= Infinitesimal unitary transformation
{title2=$U(\epsilon)=I+i\epsilon F+O(\epsilon^2)$}

Differentiating a <unitary operator> family at the identity gives an anti-Hermitian tangent. In the convention $U(\epsilon)=I+i\epsilon F+O(\epsilon^2)$ for real $\epsilon$, the generator $F$ is <Hermitian>. This is the one-parameter version of the <Hermitian quantum generator convention>. A finite linear truncation need not itself be exactly unitary.

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