Matrix representation in QM Assignment -- Need some help please

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SUMMARY

The discussion focuses on the construction of matrices for spin operators Sx, Sy, and Sz using the eigenstates |x+⟩ and |x−⟩ as a new basis. The original matrices for the spin operators in the |z⟩ basis are provided as Sx^=ℏ/2(0,1,1,0), Sy^=ℏ/2(0,i,−i,0), and Sz^=ℏ/2(1,0,0,−1). The user correctly derives the eigenstates |x+⟩ and |x−⟩ from |z+⟩ and |z−⟩, and seeks validation of their method for evaluating the Sx operator and guidance on evaluating Sy and Sz operators.

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Ashish Somwanshi
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Homework Statement
In the lecture, we used the eigenstates |z+⟩ and |z−⟩ of Sz^, we obtained the matrices for spin operators

Sx^=ℏ/2(0,1,1,0) Sy^=ℏ/2(0,i,−i,0) Sz^=ℏ/2(1,0,0,−1)
note: the numbers in brackets are 2×2 matrices!!!


Now use the eigenstates of |x+⟩ and |x−⟩ of Sx^,as a new basis, construct matrices for the spin operators Sx^, Sy^ and Sz^.
Relevant Equations
Both Question and Relevant equations are posted below in attempt.
This screenshot contains the original assignment statement and I need help to solve it. I have also attached my attempt below. I need to know if my matrices were correct and my method and algebra to solve the problem was correct...
Screenshot_20221008_235549.jpg
 

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Ashish Somwanshi said:
Homework Statement:: In the lecture, we used the eigenstates |z+⟩ and |z−⟩ of Sz^, we obtained the matrices for spin operators

Sx^=ℏ/2(0,1,1,0) Sy^=ℏ/2(0,i,−i,0) Sz^=ℏ/2(1,0,0,−1)
note: the numbers in brackets are 2×2 matrices!Now use the eigenstates of |x+⟩ and |x−⟩ of Sx^,as a new basis, construct matrices for the spin operators Sx^, Sy^ and Sz^.
Relevant Equations:: Both Question and Relevant equations are posted below in attempt.

I have also attached my attempt below.
Please make it a habit to post your work using LaTeX, and not in blurry attached pictures. There is a "LaTeX Guide" link below the Edit window to help you learn LaTeX. Thank you.
 
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My solution to above assignment goes like this:

Since
| ×±> = 1/ sqrt(2) |z+> ± 1/sqrt(2) |z->

|x+> = 1/sqrt (2) |z+> + 1/sqrt(2) |z->
|x-> = 1/sqrt(2) |z+> - 1/sqrt(2) |z->

So eigenvalue equations are:

Sx |x+> = 1/sqrt(2) { |z+> + |z->}
Sx |x-> = 1/sqrt(2) { |z+> - |z->}

So we can represent Sx operator in matrix form as:

Sx = 1/sqrt(2)*
|z+> + |z->0
0|z+> - |z->

Is my method to evaluate Sx operator from the relationship between x and z correct? Also how can I evaluate Sy and Sz operators for spin.?
 
Last edited:

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