Strong classical simulation

[bichselb]

Hi

I would like to use this implementation for strong classical simulation, as discussed in here.

I am not quite sure how I have to proceed. Assuming I have a QASM circuit in a text file, I assume I can use functions load and to_graph to obtain the corresponding VecGraph.

But how do I get the probability of a given output? I assume I have to use full_simp somehow, but do not know how to get a number from it, or how to specify which output probability I am looking for.

Thanks for your help!

[akissinger]

Hi,

It's the Decomposer you want for computing amplitudes (or probabilities). Have a look at the code in bin/ for some examples (e.g. things named "hidden shift" or "pauli gadget").

In summary: load a circuit and convert it to a graph with to_graph. Then, you can plug bra's and ket's into the inputs/outputs of a graph using the plug_inputs and plug_outputs methods, pass that graph to the decomposer, then retrieve the scalar:

g.plug_inputs(&vec![BasisElem::Z0; 20]);
g.plug_outputs(&vec![BasisElem::Z0; 20]);
let mut d = Decomposer::new(&g);
d.with_full_simp(); // set simplification method to full_simp
// optionally adjust some other parameters...
d.decomp_all();
println!("<0..0|C|0..0> = {}", d.scalar.float_value());

[bichselb]

Thanks so much, this works!