I'm running a quantum simulation and want to obtain some information from a single shot of an experiment. Here's part of the code I'm working on:

for i in range(Nshot):
    Expeb = []
    for measure_circuit in [circ_1, circ_2, circ_3, circ_4]:
        measure_circuit = transpile(measure_circuit,backend=backend,optimization_level=2,initial_layout = [1])
        counts = execute(measure_circuit, backend = backend, shots=1).result().get_counts()
        for output in ['0','1']:
            if output not in counts:
                counts[output] = 0
        expe = (counts['0'] - counts['1']) 
    Est = sum(x*y for x,y in zip(Expeb,[a,b,c,d]))

The code works on simulators, but it might take a very long time if Nshot gets large (Like 5000, I think that's because I generated a lot of circuits) and I submit the jobs to a quantum device. I wonder is there a way I can extract information (like making calculations for) a single shot but in a more efficient way? Thanks for the help!

  • $\begingroup$ If I understand your question correctly, then in general this is probably not the case since a single shot won't give you enough statistic. $\endgroup$
    – KAJ226
    Aug 9, 2021 at 16:20
  • $\begingroup$ @KAJ226 Thanks for the comment! I want to do some calculations from the results of a single shot and repeat the process many times to get more statistics:) (shots = 1, but Nshot could be large) $\endgroup$
    – ZR-
    Aug 9, 2021 at 16:24
  • $\begingroup$ Ah, I see what you mean now. I should note that if this is the case then this means you have to resubmit the circuit from start every time... which adds a lot of overhead time (validation etc...) $\endgroup$
    – KAJ226
    Aug 9, 2021 at 18:10
  • $\begingroup$ @KAJ226 Haha thanks! $\endgroup$
    – ZR-
    Aug 9, 2021 at 18:51

1 Answer 1


You can use memory option. It will make the per-shot measurement bit-strings returned in the result:

memory = execute(measure_circuit, backend = backend, memory = True, shots = 1024).result().get_memory()
  • 1
    $\begingroup$ Thanks for the answer! I just checked out the document here: qiskit.org/documentation/stubs/…. Does the length of bitstring represents how many qubits you have, and the length of the returned list represents the number of shots? $\endgroup$
    – ZR-
    Aug 9, 2021 at 16:45
  • 1
    $\begingroup$ Yes. For 1024 shots, the returned list will contain 1024 entries. $\endgroup$ Aug 9, 2021 at 16:50
  • $\begingroup$ Awesome! Thank you! $\endgroup$
    – ZR-
    Aug 9, 2021 at 16:54

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