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Equation 1 · Part 2 · How Fast Can a Horizon Learn Which Path You Took?

Symbol h_rm in

∣Ψ(0)⟩=∣0⟩+∣1⟩2⊗∣hin⟩.|\Psi(0)\rangle= \frac{|0\rangle+|1\rangle}{\sqrt 2}\otimes|h_{\rm in}\rangle .
hinh_{\rm in}

What this part means

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

Its job in the formula

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

The passage around this formula

Begin with an equal superposition of two localized alternatives, ∣Ψ(0)⟩=∣0⟩+∣1⟩2⊗∣hin⟩|\Psi(0)\rangle= \frac{|0\rangle+|1\rangle}{\sqrt 2}\otimes|h_{\rm in}\rangle . The labels zero and one denote paths, not energy eigenstates. After the system’s long-range field interacts with the inaccessible degrees of freedom, an idealized final pure state has the form

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A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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