Change of Basis: Converting Wavefunction from S_z to S_x

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Discussion Overview

The discussion centers on the conversion of a wavefunction from the S_z basis to the S_x basis in quantum mechanics, specifically addressing the method of using rotation operators for this transformation. The scope includes theoretical and conceptual aspects of quantum state representation.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant inquires about the method for converting a wavefunction expressed in the S_z basis to the S_x basis, seeking a simple approach.
  • Another participant suggests that a rotation operator could be used to achieve this conversion.
  • A third participant confirms that a rotation of π/2 radians about the y-axis is the correct approach to convert from S_z to S_x.
  • A later reply questions this approach, expressing confusion about whether the resulting state vector should be a superposition of +x and -x states, rather than a pure state, after applying the rotation operator.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the resulting state vector after the conversion, indicating a lack of consensus on whether the output should be a superposition or a pure state.

Contextual Notes

There is uncertainty regarding the assumptions made about the state vector's representation and the implications of the rotation operator used in the conversion process.

Norman
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Hello all,

I need some help...
If I know the form of a wavefunction in the [itex]S_z[/itex] basis, say it is spin up, how do I convert that to a wavefunction expressed in the [itex]S_x[/itex] basis? Is there a very simple way to do this?
Thanks
 
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Anyone?
Do I just rotate the spinor using a rotation operator?
Help?
 
You've basically got it. To convert from Sz to Sx, you rotate the state vector p/2 rad about the y-axis.
 
Tom Mattson said:
You've basically got it. To convert from Sz to Sx, you rotate the state vector p/2 rad about the y-axis.

Hi, I know this is old. I am sorry, but I have some confusion about this.

I wonder, shouldn't the new state vector be a superposition of +x and -x? If I apply the rotation operator to my z state I get a pure state.

Where has my thinking gone wrong?
 

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