Symbol E

Its job in the formula

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

Where the article explains it

Read against that schema, the variational loop’s mapping is direct rather than metaphorical in its outline: the parameter vector $\theta$ is a genotype; the measured expectation value E($\theta$) is a fitness score, evaluated by a fitness oracle that happens to require physical qubits rather than a spreadsheet; and the classical update rule is a selection-and-variation operator proposing the next candidate.

Learn the underlying idea

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

Open the illustrated functions: inputs become outputs guide →