2. Let ψ1 and ψ2 denote the normalized eigenfunctions of particle with...
Solution:
To find the shortest time T at which ψ(t = T) will be orthogonal to ψ(t = 0), we need to consider the time evolution of the state ψ(t).
Time Evolution of a Quantum State:
The time evolution of a quantum state ψ(t) is given by the Schrödinger equation:
iħ(dψ(t)/dt) = Hψ(t)
where i is the imaginary unit, ħ is the reduced Planck's constant, and H is the Hamiltonian operator of the system.
Given Information:
We are given that ψ1 and ψ2 are the normalized eigenfunctions of a particle with energies E1 and E2 respectively, where E2 > E1. Also, at t = 0, the particle is prepared in the state ψ(t = 0) = 1/√2(ψ1 + ψ2).
Time Evolution of ψ(t = 0):
Using the time evolution operator, we can find the state ψ(t) at any time t:
ψ(t) = e^(-iHt/ħ)ψ(t = 0)
Finding the Orthogonality Condition:
To find the shortest time T at which ψ(t = T) is orthogonal to ψ(t = 0), we need to calculate the inner product of ψ(t = 0) and ψ(t = T) and set it to zero:
⟨ψ(t = 0)|ψ(t = T)⟩ = 0
Calculating the Inner Product:
Using the time evolution operator, we can calculate ψ(t = T):
ψ(t = T) = e^(-iHT/ħ)ψ(t = 0)
Now, let's calculate the inner product:
⟨ψ(t = 0)|ψ(t = T)⟩ = ⟨ψ(t = 0)|e^(-iHT/ħ)ψ(t = 0)⟩
Applying the Orthogonality Condition:
Setting the inner product to zero, we have:
⟨ψ(t = 0)|e^(-iHT/ħ)ψ(t = 0)⟩ = 0
Calculating the Exponential:
To simplify the calculation, let's express the exponential term as a power series:
e^(-iHT/ħ) = 1 - (iHT/ħ) + (1/2!)(iHT/ħ)^2 - (1/3!)(iHT/ħ)^3 + ...
Substituting this into the inner product expression, we get:
⟨ψ(t = 0)|(1 - (iHT/ħ) + (1/2!)(iHT/ħ)^2 - (1/3!)(iHT/ħ)^3 + ...)ψ(t = 0)⟩ = 0
Calculating the Inner Product:
Expanding the inner product, we have:
⟨ψ(t = 0)|ψ(t = 0)⟩ - (iHT/ħ)⟨ψ(t = 0)|ψ