Code imitating like max-cut(qaoa)

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1

QAOA for MaxCut | PennyLane Demos

i want to write a piece of code by imitating the max-cut，i have some questions
in max-cut：

def objective(params):
    gammas = params[0]
    betas = params[1]
    neg_obj = 0
    for edge in graph:
        # objective for the MaxCut problem
        neg_obj -= 0.5 * (1 - circuit(gammas, betas, edge=edge, n_layers=n_layers))
    return neg_obj

so 【circuit(gammas, betas, edge=edge, n_layers=n_layers) 】= qml.PauliZ(edge[0]) @ qml.PauliZ(edge[1]) ?

and if my cost fuction is Hc=const1 * qml.PauliZ(wire0) @ qml.PauliZ(wire1) + const2 * qml.PauliZ(wire0) how should i write here?

neg_obj -= circuit(gammas, betas, n_layers=n_layers) ?

thank you for your reply！

2

Hi @ming ! If your cost function does not depend on edges, and you simply want to minimize that hamitlonian, you could express the code like this:

def objective(params):
    gammas = params[0]
    betas = params[1]
    return  -circuit(gammas, betas, edge=edge, n_layers=n_layers)

In addition, you will have to update the line where you define the Hamiltonian in the circuit. Hope this solve your question :slight_smile:

3

Thank you for your reply!but If my cost function does not depend on edges,why can’t I just delete the “edge”?

4

Hey @ming! You can most certainly get rid of edge if circuit doesn’t depend on it whatsoever :slight_smile: