## Algorithm for Gradient Descent Disentangler

General discussions on the ideas behind the algorithm.
gunheepark0229
Posts: 9
Joined: 15 May 2020, 10:52

### Algorithm for Gradient Descent Disentangler

Hi! I was checking the documents for the Gradient Descent Disentangler, and I had some concepts that I cannot understand.
The document says $$dS = {\partial S(Utheta,n)} / {\partial U}$$

R[i] is given by $${\partial S(Y,n)} / {\partial Y_i}$$

The point I cannot understand is how dS is given by:

Code: Select all

|     .----X--R--Z----.
|     |    |     |    |
|     |    q0    q1   |
|     |               |
|     |    q0*   q1*  |
|     |    |     |    |
|     .----X*-Y--Z*---.

Furthermore, is applying exp(- tdS) a heuristic way to update U?
Usually, some variable w is updated by $${w_{new} = w - \eta dS/dw}$$, but in our case, we need to keep U unitary, so we are applying unitary exponentials (if dS is anti-hermitian).
Is it a correct approach?