Fix: Potential Data Leakage in Quantum Data Tutorial.

[OkuyanBoga]

A solution to potential data leakage in #828.

Instead of concatenating train and test sets, they should be separately dealt with when getting a stilted dataset:

In lines L745-752:

y_train_new = get_stilted_dataset(S_pqk, V_pqk, S_original, V_original)
y_test_new = get_stilted_dataset(S_pqk_test, V_pqk_test, S_test_original, V_test_original)

where spectrum is calculated separately for test set:

S_pqk_test, V_pqk_test = get_spectrum(
    tf.reshape(x_test_pqk, [-1, len(qubits) * 3]))

S_test_original, V_test_original = get_spectrum(
    tf.cast(x_test, tf.float32), gamma=0.005)

print('Eigenvectors of pqk kernel matrix for test:', V_pqk_test)
print('Eigenvectors of original kernel matrix for test:', V_test_original)

Closes #828.

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[mhucka]

@OkuyanBoga Thank you for this contribution. Would you be able to resolve the (simple) conflicts that have arisen? I will then review the PR.

[mhucka]

Closing due to age and nonresponse.

[OkuyanBoga]

Hi, sorry for late response but I think the issue I shown here breaks the whole tutorial. If there is not a leakage, the performance of the method reduces significantly.

Any suggestions or comments?

[mhucka]

@OkuyanBoga Thanks for your reply and raising awareness of the problem. I reopened this PR.

It looks like it's close to being mergeable, but there are differences in the .ipynb file that are not part of the actual changes. This is a separate mater from the 188 commit difference that GitHub also reports – the actual changes to the file are much smaller. However, there are still irrelevant changes in the .ipynb file, e.g. to metadata elements in the .ipynb file. Before merging, we'd like to make the diff as small as possible so that the change history is easier to follow in the future.

One way may be to click "resolve conflicts" here on this PR page, then out of the 8 changes that GitHub notes in the diff view, accept your incoming changes just for the ones that matter.