The Efficient SU2 is calculated wrong after CNOT and also the end state

[sudikiniirs]

URL to the relevant course

https://quantum.cloud.ibm.com/learning/en/courses/quantum-machine-learning/data-encoding#efficient-su2

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• new content request
• typo
• code bug
• out-of-date content
• broken link
• other

Describe the fix or the content request.

The state representation is wrong in Efficient SU2 after the application of CNOT gate and henceforth the end state representation is also wrong. I am attaching a board work kindly see the state psi2 for the correct state representation of the states and the end state hence forth. Kindly update it with new and correct content. If I am wrong kindly mail pointing out where I am wrong at sudikin.iitrpr@gmail.com. Thank you.

Best regards,

Sudikin Pramanik
PhD Scholar
Quantum Machine Learning
IIT Ropar
India

For new content requests - if the request is accepted, do you want to write the content?

I will write (or already have written) a draft of the proposed content

[christopherporter1]

@sudikiniirs thank you for noticing this! I agree with your assessment, and I obtain the same answer you have. I opened a PR to correct this (#4021). There will be very minor differences compared to your solution for two reasons: 1) I pulled out a few more factors than you, but more importantly 2) I updated the notation to match standard Qiskit notation in which the least-significant qubit goes to the far right, as in |q_1, q_0> (which was not done in the original text). So your term |10> will look like my term |01>, but they are otherwise in agreement. Thank you again! One can see from the whiteboard how much work it was, and now I also know first-hand!

[sudikiniirs]

Thank you so much. This inspires scholars to do good work.