B Can the probabilities of state vectors |r⟩ and |i⟩ be determined from |ψ⟩?

[hongseok]

TL;DR

∣r⟩,∣l⟩,∣i⟩, and ∣o⟩ can all be expressed as expressions for ∣u⟩ and ∣d⟩. So, given the state vector ∣ψ⟩ = α∣u⟩ + β∣d⟩, is it possible to know not only the probability of ∣u⟩ but also the probability of ∣r⟩ and ∣i⟩? ∣ψ⟩ can be expressed as an expression for ∣r⟩, ∣l⟩ or ∣i⟩, ∣o⟩.

∣r⟩,∣l⟩,∣i⟩, and ∣o⟩ can all be expressed as expressions for ∣u⟩ and ∣d⟩. So, given the state vector ∣ψ⟩ = α∣u⟩ + β∣d⟩, is it possible to know not only the probability of ∣u⟩ but also the probability of ∣r⟩ and ∣i⟩? ∣ψ⟩ can be expressed as an expression for ∣r⟩, ∣l⟩ or ∣i⟩, ∣o⟩.

 

[Nugatory]

So, given the state vector ∣ψ⟩ = α∣u⟩ + β∣d⟩, is it possible to know not only the probability of ∣u⟩ but also the probability of ∣r⟩ and ∣i⟩? ∣ψ⟩ can be expressed as an expression for ∣r⟩, ∣l⟩ or ∣i⟩, ∣o⟩.

You haven't said what any if any observable corresponds to any of these vectors, so all we can give you is the general answer:
If we can write $$|\psi\rangle=\alpha_1|A_1\rangle+\alpha_2|A_2\rangle=\beta_1|B_1\rangle+\beta_2|B_2\rangle$$ where $|A_1\rangle$ and $|A_2\rangle$ are orthogonal eigenvectors of the Hermitian operator $\hat{A}$ and likewise for $|B_1\rangle$ and $|B_2\rangle$ and the observable $\hat{B}$ then ...

Yes, we know the probability of getting any of these four possible results if we were to perform the measurement. The catch is that if $\hat{A}$ and $\hat{B}$ do not commute we only get to measure one of them.

 

[anuttarasammyak]

TL;DR Summary: ∣r⟩,∣l⟩,∣i⟩, and ∣o⟩ can all be expressed as expressions for ∣u⟩ and ∣d⟩. So, given the state vector ∣ψ⟩ = α∣u⟩ + β∣d⟩, is it possible to know not only the probability of ∣u⟩ but also the probability of ∣r⟩ and ∣i⟩? ∣ψ⟩ can be expressed as an expression for ∣r⟩, ∣l⟩ or ∣i⟩, ∣o⟩.

∣r⟩,∣l⟩,∣i⟩, and ∣o⟩ can all be expressed as expressions for ∣u⟩ and ∣d⟩. So, given the state vector ∣ψ⟩ = α∣u⟩ + β∣d⟩, is it possible to know not only the probability of ∣u⟩ but also the probability of ∣r⟩ and ∣i⟩? ∣ψ⟩ can be expressed as an expression for ∣r⟩, ∣l⟩ or ∣i⟩, ∣o⟩.

The probability that the state is |r> in observation is
|<r|\psi>|^2=|\alpha<r|u>+\beta<r|d>|^2
in condition that all these bras and kets are normalized.