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Equation 40 · Part 2 · The Bit Comes Back Before the Bearing

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g−2g^{-2}
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What this part means

A raised number can be a power. When it is a label or bound, it selects a case or the upper limit of a sum; the formula’s structure distinguishes these uses.

Its job in the formula

A raised mark can be a power or an index. Its position and the surrounding notation determine which.

The passage around this formula

FQF_Q is the quantum Fisher information of the radiation’s reduced state with respect to g ; it carries units of g−2g^{-2} , i.e. inverse radians squared, and since g is already dimensionless, FQF_Q is a pure number. δ\delta is the alignment tolerance the observer has decided to demand, also in radians, and tG(δ)t_G(\delta) has units of time [ 12 ] . This bound is achievable asymptotically by the symmetric logarithmic derivative measurement; nothing here claims it is achieved by any specific realizable circuit, only that it is the correct floor no circuit can beat.

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Learn the underlying idea

An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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Sources cited in the surrounding passage

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