IonQ Harmonium gives probability of a single qubit circuit output as "1" while the same circuit on IonQ Simulator correctly shows 50/50

Question

As described in the title. I have a simple circuit with a qubit that is being measured. I expect that the Result object show probabilities as [{"1": 0.5},{"0":0.5}] but instead I receive:

[ExperimentResult(shots=1, success=True, meas_level=2, data=ExperimentResultData(counts={'1': 1}, probabilities=defaultdict(<class 'int'>, {'1': 1})), header=QobjExperimentHeader(qiskit='True', name='circuit-88', num_qubits='1')))]

The same circuit submitted to IonQ.simulator gives the correct probabilities.

Looks like a bug on IonQ side?

Answer 1

Hello, @Grzegorz Górnicki !

Apologies for the late reply! The AI generated answer should have been validated and marked by the poster which has caused some delays.

Why am I getting a probability of 1 instead of 50/50 as expected?

In this case, the experiment was run for only 1 shot (shots=1):

[ExperimentResult(shots=1, success=True, meas_level=2, data=ExperimentResultData(counts={'1': 1}, probabilities=defaultdict(<class 'int'>, {'1': 1})), header=QobjExperimentHeader(qiskit='True', name='circuit-88', num_qubits='1')))]

The expected result for a single shot would always be 100% for 0 or 1. Since the qubit is measured on a real quantum computer, it will give the distribution of the actual results. For 1 shot you would get a single result while for more shots (iterations), you would expect the distribution to be more split.

The IonQ simulator returns more idealized results so it will show a perfect distribution regardless of the number of shots.

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