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Equation 96 · Part 2 · The Atlas That Refuses to Close

Symbol i

∣f⟩=12(∣↑⟩+i∣↓⟩)|f\rangle = \tfrac{1}{\sqrt2}(|{\uparrow}\rangle+i|{\downarrow}\rangle)
ii

What this part means

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

Its job in the formula

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

The passage around this formula

​ 1 ​ ( ∣ ↑ ⟩ + ∣ ↓ ⟩) , and postselect along y , |f⟩\rangle = 12(∣↑⟩+i∣↓⟩)\tfrac{1}{\sqrt2}(|{\uparrow}\rangle+i|{\downarrow}\rangle) . Then ⟨\langle f|ψ\psi⟩\rangle = 12(1−i)\tfrac12(1-i) and ⟨\langle f|σz\sigma_z|ψ\psi⟩\rangle = 12(1+i)\tfrac12(1+i) , so the weak value of σz\sigma_z is

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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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