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I calculated the probabilities for two measurements using mid-circuit measurements feature in IBMQ by following circuit:

qc_simp = QuantumCircuit(1,2)
qc_simp.h(0)
qc_simp.barrier([0])
qc_simp.measure([0], [0])
qc_simp.barrier([0])
qc_simp.measure([0], [1])

enter image description here

However, I get the following histogram for two measurements:

Meas 1 result:  {'0': 487, '1': 537}
Meas 2 result:  {'0': 9, '1': 1015}

Why does the second histogram doesn't give "equal" probabilities for '0' and '1'? IBMQ device used: ibm_armonk

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    $\begingroup$ I can't seem to reproduce the problem. Can you please provide the way you initialize your backend, run your circuit and retrieve your results with it please? Just some kind of a MWE that we can copy, paste and run to ease debugging! $\endgroup$ Jan 6 at 10:28
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    $\begingroup$ I agree with the fact that is is clearly not the expected behaviour, did you test your circuit on other backends by any chance? Just to check if this is happening only on this backend or also on others! $\endgroup$
    – Lena
    Jan 6 at 14:43
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    $\begingroup$ I can see the correct behavior with a different backend. $\endgroup$ Jan 7 at 11:35
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    $\begingroup$ In that case my best guess would be that there is an issue with the backend, if you are already in the Qiskit Slack then I would suggest posting your question on the #ibm-q-systems channel so you'll have the attention of people that can take care of the problem :) $\endgroup$
    – Lena
    Jan 10 at 8:48

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