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Equation 19 · The Entry a Relabeling Cannot Write

What does this equation mean?

Λ†(Ic)=If\Lambda^\dagger(I_c) = I_f

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Inputs and operationsI_f
Result or conditionLambda^dagger(I_c)
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This equation states an equality: the expressions on both sides have the same value under the article’s assumptions. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.

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Λ†\Lambda^\dagger

Symbol Lambda^dagger

the define.

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IcI_c

Symbol I_c

IcI_c is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

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IfI_f

Symbol I_f

IfI_f is an input to the expression that computes the quantity on the left.

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=

=

The expressions on both sides represent the same quantity under the stated assumptions.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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How to interpret it

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What the article says around this equation

Λ†\Lambda^\dagger is positive because Λ\Lambda is completely positive and every Λ(ρ)\Lambda(\rho) with ρ\rho ≥\ge 0 is itself a valid state; it is unital, Λ†(Ic)\Lambda^\dagger(I_c) = IfI_f , because Λ\Lambda preserves trace for every input. This duality is the same construction Stinespring used to show that any completely positive map admits a dilation to a larger, unitary description [ 9 ] , and it lets a coarse Hamiltonian be pulled back onto the fine space without the fine space’s own structure ever being disturbed.

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