Equation 86 · Part 4 · The Entry a Relabeling Cannot Write

Symbol e

|\psi(t)\rangle = \cos(gt)\,|e,g\rangle - i\sin(gt)\,|g,e\rangle,

e

What this part means

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

Its job in the formula

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

Full expressionSymbol eArticle meaning

The passage around this formula

…- $\sin^2(gt)$ ] = ( $\hbar$ $\omega$ /2) $\cos(2gt)$ , while $\langle$ $H_f$ $\rangle$ is exactly time-independent — a general fact for any state evolving under its own generator, not special to this one — and equal here to $\langle$ e,g| $H_f$ |e,g $\rangle$ = $\hbar$ $\omega$ /2 - $\hbar$ $\omega$ /2 + 0 = 0 , since $H_{SB}$ is purely off-diagonal in this basis. The ledger reading follows immediately:

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Learn the underlying idea

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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Sources cited in the article section

[12] Circuit Quantum Electrodynamics ↗

These citations provide research context; check each source for the exact claim it supports.