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Equation 9 · Part 3 · How Fast Can a Horizon Learn Which Path You Took?

Symbol V

D(T)=1−V(T)2,V(T)2+D(T)2=1.D(T)=\sqrt{1-V(T)^2}, \qquad V(T)^2+D(T)^2=1.
VV

What this part means

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

Its job in the formula

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

The passage around this formula

For two pure states, D(T)=1−V(T)2,V(T)2+D(T)2=1D(T)=\sqrt{1-V(T)^2}, \qquad V(T)^2+D(T)^2=1. This is the first translation. A visibility of 0.6 corresponds to a trace distinguishability of 0.8; neither number is a bit count.

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Learn the underlying idea

A function assigns an output to each allowed input. The expression f(x) means “apply f to x”.

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Sources cited in the article section

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