Design NISQ Circuit with StrawberryFields

Question

I am trying to design this circuits with strawberry fields. However I could not connect my first and second qubit mode:

orange boxes are beam splitters, blue boxes are phase shifters. The green box is nothing. (There was a letter of brand so I wanted to close it) First two lines corresponds to 2 modes of my first qubit: Let's say: 0_a and 1_a and the other two lines corresponds my second qubit modes Let's say 0_b and 1_b

My code is here:

  prog = sf.Program(4)

with prog.context as q:
    ops.BSgate() | (q[0], q[1])
    ops.BSgate() | (q[2], q[3])
    ops.Rgate(0.5719) | q[0]
    ops.BSgate() | (q[0], q[1])
    ops.Rgate(-1.9782) | q[1]
    ops.BSgate() | (q[0], q[1])
    ops.Rgate(-1.9782) | q[2]
    ops.BSgate() | (q[2], q[3])
    ops.Rgate(-1.9782) | q[2]
    ops.BSgate() | (q[2], q[3])
eng = sf.Engine("fock", backend_options={"cutoff_dim": 5})

prog.print()
#prog.draw_circuit(tex_dir='./circuit_tex', write_to_file=True)

My result is here

and indeed I could not make this connection:

Any help for me? Am I writing to correct code?

Answer 1

Ok It is done and it is correct. I just forgat to give an initial state to the program like

Ket(initial_state) | q 

And after that I also added a BSGate for 1 and 2 mode