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Equation 3 · Part 1 · The Bit Comes Back Before the Bearing

Symbol psi

∣ψ(g)⟩|\psi(g)\rangle
ψ\psi

What this part means

psi is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Its job in the formula

psi is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

The passage around this formula

Into this old hole go two systems. The first, A , is a two-dimensional qubit prepared in an arbitrary, unknown state and coupled to nothing the hole’s own symmetries track — a spectator, chosen so that its recovery is the cleanest possible test of the Hayden-Preskill mechanism on its own terms. The second, C , is a compass: a physical carrier prepared in a state |ψ(g)\psi(g)⟩\rangle that transforms under a one-parameter group of rotations generated by a Hermitian charge J^\hat J , the same charge the hole’s own angular momentum is built from,

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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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