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Equation 96 · Part 2 · The Bit Comes Back Before the Bearing

Symbol g

FQ=4[⟨∂gψ∣∂gψ⟩−∣⟨ψ∣∂gψ⟩∣2]=4ℏ2Var⁡J^,F_Q = 4\Big[\langle\partial_g\psi|\partial_g\psi\rangle - |\langle\psi|\partial_g\psi\rangle|^2\Big] = \frac{4}{\hbar^2}\operatorname{Var}\hat J,
gg

What this part means

g is one of the signed contributions combined to compute the quantity on the left.

Its job in the formula

g is one of the signed contributions combined to compute the quantity on the left.

The passage around this formula

…on its own heading. After scrambling, that fixed total has to be reconstructed piecemeal from radiation, and each individually emitted quantum, to the extent it is only weakly and independently correlated with g once the hole’s own state is traced over, contributes an addition to the total that adds like an independent sample rather than like a decoded codeword. This is the standard-quantum-limit regime of parameter estimation: for N independent, identically prepared probes each with per-probe Fisher…

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A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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