I am looking to implement Quantum PCA from this paper (page 62). They have their code on Github.
I have gone through the paper multiple times but failing to understand how they got numbers (for theta, phi and lambda) on line 6, 7, 10, 11, 12 and 13. I understand classical pre-processing where they calculate covariance matrix, density matrix and purify density matrix. I fail to understand how they get those numbers (for theta, phi and lambda) from purified density matrix.
If anyone can point me on how to calculate theta, phi and lambda.
Thanks in advance!