I am implementing an Ising chain over 8 qubits. It involves pair-wise CNOT between all the qubits. In the first time step, I am doing CNOTs between qubits 0 and 1, 2 and 3, 4 and 5, and 6 and 7. In the second time step, I would do CNOTs between qubits 1 and 2, 3 and 4, and 5 and 6. I have written the code as follows:

# Block A for the first time step

# Block B for the second time step

I would like the gates in Block A to be applied simultaneously. Then, in the next step, gates in Block B should be applied simultaneously. How to convey to the compiler that I do not want the above written code to be compiled sequentially, rather I want it to be applied block-wise.

  • $\begingroup$ Why does not suit barrier between the blocks? $\endgroup$
    – Psanfi
    Commented Aug 22, 2020 at 17:19

1 Answer 1


Did you try to put a barrier between your two blocks? You can do this by writing this qp.barrier() right after your first block, then Qiskit will transpile separately the two blocks. Is this what you were searching for?

  • $\begingroup$ Thanks, this was really helpful. $\endgroup$ Commented Aug 26, 2020 at 14:37
  • $\begingroup$ @SHASHANKRANU happy to see so, could you maybe accept the answer? Thanks :) $\endgroup$
    – Lena
    Commented Aug 27, 2020 at 7:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.