phy-4600/solutions/chap5/prob2

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A particle in an infinite square well has an initial state vector
❙Ψ(t=0)❭ = A(❙φ₁❭ - ❙φ₂❭ + ι❙φ₃❭).
where ❙φₙ❭ are the energy eigenstates. This also means
❬Ψ(t=0)❙ = A⃰(❬φ₁❙ - ❬φ₂❙ + ι❬φ₃❙)
❙Ψ(t=0)❭ = _͟A͟ (αβ❙φ₁❭ - βγ❙φ₂❭ + αγι❙φ₃❭)
αβγ
In the energy basis,
❙φ₁❭ ≐ ⎛1⎞ ❙φ₂❭ ≐ ⎛0⎞ and ❙φ₃❭ ≐ ⎛0⎞
⎜0⎟ ⎜1⎟ ⎜0⎟
⎝0⎠, ⎝0⎠, ⎝1⎠.
So,
❙Ψ(t=0)❭ ≐ ⎛ A ⎞
⎜-A ⎟
ιA ⎠.
(𝐚) Multiplying the state vector by its magnitude normalizes it.
❙Ψ′(t=0)❭ ≐ __͟A͟__ ⎛ 1 ⎞ = _͟1͟ ⎛ 1 ⎞
√(3A²) ⎜-1 ⎟ √3 ⎜-1 ⎟.
ι ⎠ ⎝ ι