← Mathematical compendium

Published equation contexts

Aw=⟨f∣A^∣ψ⟩⟨f∣ψ⟩A_w = \frac{\langle f|\hat A|\psi\rangle}{\langle f|\psi\rangle}

Why this formula appears here

There is a fifth kind of answer to “where,” and it is worth stating precisely how it differs from all four above before using it. Prepare a system in a state |ψ\psi⟩\rangle , couple it weakly to a pointer, and then postselect on a final state |f⟩\rangle measured after the coupling. The weak value of any observable A^\hat A , position among them, conditioned on that postselection is Aw=⟨f∣A^∣ψ⟩⟨f∣ψ⟩A_w = \frac{\langle f|\hat A|\psi\rangle}{\langle f|\psi\rangle}. introduced by Aharonov, Albert, and Vaidman as the quantity a weakly coupled pointer’s mean shift actually reports, to leading order in the coupling strength, once the postselection has been performed [ 11 ] . AwA_w is not an eigenvalue of A^\hat A , not an expectation value in the ordinary sense, and…

Read the full article-specific guide →

Read the representative guide

⟨f∣A^∣ψ⟩\langle f|\hat A|\psi\rangle

Numerator: langle f|hat A|psirangle

The complete quantity above the fraction bar.

Read this term in its guide →
⟨f∣ψ⟩\langle f|\psi\rangle

Denominator: langle f|psirangle

The complete quantity below the fraction bar; it must be nonzero for this division.

Read this term in its guide →

How to interpret it

With a fixed numerator, increasing a nonzero denominator reduces the fraction. Read it with the definitions, units, and assumptions supplied by the article.

Research cited beside this formula

Learn the mathematics behind it

Published contexts (1)

A symbol can carry a different meaning in another article. Each occurrence keeps its own guide and term definitions.

Aw=⟨f∣A^∣ψ⟩⟨f∣ψ⟩,A_w = \frac{\langle f|\hat A|\psi\rangle}{\langle f|\psi\rangle},

Equation 90 · Evolutionary Physics

The Atlas That Refuses to Close

This equation states an equality: the expressions on both sides have the same value under the article’s assumptions.

There is a fifth kind of answer to “where,” and it is worth stating precisely how it differs from all four above before using it. Prepare a system in a state |ψ\psi⟩\rangle , couple it weakly to a pointer, and then postselect on a final state |f⟩\rangle measured after the coupling. The weak value of any observable A^\hat A , position among them, conditioned on that postselection is Aw=⟨f∣A^∣ψ⟩⟨f∣ψ⟩A_w = \frac{\langle f|\hat A|\psi\rangle}{\langle f|\psi\rangle}. introduced by Aharonov, Albert, and Vaidman as the quantity a weakly coupled pointer’s mean shift actually reports, to leading order in the coupling strength, once the postselection has been performed [ 11 ] . AwA_w is not an eigenvalue of A^\hat A , not an expectation value in the ordinary sense, and…

Meanings in this article

Equation guide → · Article →