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When I execute the following circuit, I expect that in both classical registers, the content is identical.

q = QuantumRegister(1)
c = ClassicalRegister(2)
circuit = QuantumCircuit(q, c)
circuit.h(q[0])
circuit.measure(q[0], c[0])
circuit.measure(q[0], c[1])

backend = BasicAer.get_backend('qasm_simulator')
job = execute(circuit, backend, shots=100)
result = job.result()
counts = result.get_counts(circuit)

print(counts)

And the results are {'01': 44, '00': 56}, however I expect {'11': 44, '00': 56}

When I run the same circuit in the IBM Quantum Experience with the same simulator, I get the expected results.

What do I miss?

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  • $\begingroup$ Which version of Qiskit Terra are you running? $\endgroup$ – met927 Nov 6 at 10:52
  • $\begingroup$ Qiskit Terra was qiskit-terra-0.8.2 after running the update, which solved the problem I have qiskit-terra-0.10.0 now. $\endgroup$ – Daniel Müssig Nov 6 at 11:25
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When I run your code on the most recent version of qiskit I get the expected results {'11': 55, '00': 45}. It could be the case therefore that you are running an older version of qiskit and this has been fixed recently. I would suggest updating your version using pip install --upgrade qiskit

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    $\begingroup$ Thank you for the suggestion. I had installed qiskit-0.11.1 and updated to qiskit-0.13.0. $\endgroup$ – Daniel Müssig Nov 6 at 11:24

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