50 IBM A1000-113 Practice Questions: Question Bank 2025

In quantum computing, what does measuring a qubit in the computational (Z) basis return?

A developer wants to build a Bell pair using Qiskit. Which gate sequence is the standard approach (ignoring measurement)?

A team is deciding whether to use a classical bit or a qubit to represent a variable that can be both 0 and 1 until observed. Which concept best describes the qubit property they want to leverage?

In a variational quantum algorithm (VQA) workflow, which task is typically performed by the classical optimizer?

A researcher runs a circuit on real hardware and sees significantly worse results than on an ideal simulator. Which factor most directly explains this difference?

A Qiskit user wants to execute a circuit on a specific IBM Quantum device while ensuring the circuit respects the device’s connectivity and basis gates. Which approach is most appropriate?

A data scientist is considering Grover’s algorithm for searching an unstructured list of N items for a single matching item. Compared to classical exhaustive search, what is the typical scaling advantage Grover’s algorithm provides (ignoring constants)?

A developer measures a qubit immediately after applying an H gate to |0⟩ and observes roughly 50% 0s and 50% 1s over many shots. Which interpretation is correct?

A circuit run on hardware shows a strong bias toward measuring |0⟩ even when the ideal outcome should be balanced. The team suspects readout errors. Which mitigation approach most directly targets measurement (readout) errors?

A team wants to estimate the expected value ⟨Z⟩ of a single qubit at the end of a circuit on hardware. What is the correct procedure?

A new team member says measuring a qubit returns a probability (for example, 0.7) as the output value. Which statement best corrects this misunderstanding?

In Qiskit, you create a circuit with qubits but forget to include any measurements. You run it on a simulator and want classical outcomes. What is the recommended fix?

You want to create a Bell pair starting from |00⟩. Which gate sequence is the standard approach?

A researcher runs the same circuit on two different IBM Quantum backends and observes different output distributions. Both circuits compile and run successfully. What is the most likely reason for the discrepancy?

A circuit uses a two-qubit gate between qubits that are not directly connected on a chosen backend. After transpilation, the depth increases significantly. What is the primary cause?

A team is deciding whether a problem is a good candidate for a quantum algorithm at a foundational level. Which statement best captures a realistic expectation for near-term quantum devices?

You implement a variational algorithm (for example, a VQE-style workflow) and notice that increasing circuit depth improves expressivity but makes results worse on hardware. What is the best explanation?

A developer runs a circuit and sees a bias toward '0' outcomes even when the ideal simulation predicts ~50/50. They suspect readout error. Which mitigation approach most directly targets this issue?

You need to estimate the expectation value ⟨Z⟩ of a single qubit state produced by a circuit, using hardware execution. Which method is most appropriate?

A circuit’s results degrade after transpilation to a specific backend. You suspect the transpiler selected a layout that uses qubits with poor calibration (higher error rates). What is a best-practice way to address this?

A new team member claims that measuring one qubit of a 2-qubit entangled state can affect the measurement outcome statistics of the other qubit. Which statement best describes why this is possible?

In Qiskit, you want to run a circuit on real hardware and also retrieve the results for analysis. Which sequence is the most appropriate high-level workflow?

A developer is comparing classical bits and qubits. Which statement is correct?

A circuit runs successfully on a simulator but fails on a real IBM Quantum backend due to a transpilation error indicating an unsupported instruction. What is the most likely cause?

A team is deciding between a statevector simulator and a shot-based (sampling) simulator for validating an algorithm expected to produce a probability distribution over bitstrings. Which choice is best if they want to mimic hardware-like measurement statistics?

You want to estimate the expectation value ⟨Z⟩ of a single-qubit state prepared by your circuit on hardware. What is the recommended practical approach?

A circuit includes a multi-qubit controlled operation that significantly increases depth after transpilation, leading to worse performance on hardware. What is the best mitigation strategy?

A researcher runs a circuit that should produce a Bell state. On hardware, the observed counts show an unexpected number of 01 and 10 outcomes. Which explanation is most plausible?

You need to measure an observable in the X basis (Pauli-X) using hardware that measures only in the computational (Z) basis. What is the correct method?

A team is using an error-mitigation approach that assumes measurement errors can be characterized and then inverted (approximately) during post-processing. Which technique does this describe?

A new team member says, “Measuring one qubit in an entangled pair does not affect the other qubit.” Which statement best corrects this misunderstanding?

You simulate a 3-qubit circuit in Qiskit and want to view measurement results as counts of bitstrings. Which action is required to obtain counts from running the circuit?

A developer wants to increase the chance of observing the correct output bitstring from a probabilistic quantum algorithm without changing the circuit. What is the most appropriate approach?

A student confuses bit-flip and phase-flip errors. Which statement correctly describes a phase-flip error on a single qubit?

You run the same Qiskit circuit on two different IBM Quantum hardware backends and observe noticeably different output distributions. Which explanation is the most likely cause?

A team is deciding whether a problem is a good candidate for near-term quantum hardware. Which characteristic is the strongest indicator that a hybrid quantum-classical approach (e.g., variational methods) may be appropriate?

A circuit produces the correct results on an ideal simulator but shows a strong bias toward '0' outcomes on hardware, even for states expected to be balanced. Which hardware-related issue is the most plausible contributor?

A developer transpiles a circuit for a specific backend and notices the depth increased significantly. Which is the most common reason for this increase?

A researcher wants to reduce the impact of decoherence on a hardware run without changing the algorithm’s logical intent. Which strategy is generally most effective on NISQ devices?

You want to create a Bell state on two qubits and then measure both qubits in the computational basis. On real hardware, you observe outcomes '00' and '11' dominate but also see some '01' and '10'. Which explanation best matches the observation?

A new team member says, "After measuring one qubit in an entangled pair, the other qubit must already have had a definite value." Which explanation best addresses this statement at a foundational level?

A developer wants to run the same quantum circuit on multiple IBM Quantum backends and compare results in a reproducible way. Which Qiskit approach is most appropriate?

You run a circuit on hardware and see that bitstrings that are theoretically forbidden (should have probability 0) appear with small but non-zero counts. What is the most likely cause?

A team is using Grover's algorithm to search an unstructured database. They increase the number of Grover iterations beyond the recommended value and observe a worse success probability. Why does this happen?

A circuit uses two qubits that must interact via a CNOT, but the chosen backend does not have a direct coupling between those qubits. What is the most common effect of transpiling for that backend?

A researcher wants to estimate the expectation value of an observable (e.g., a Pauli operator) for a parameterized circuit using IBM Quantum. Which primitive is designed for this task?

A user runs experiments and notices a systematic bias where the device reports |0> more often than expected even when preparing |1>. Which mitigation technique most directly targets this issue?

A team is implementing a VQE workflow. They observe high variance in the estimated energy and slow convergence. Which change is most likely to reduce variance without changing the ansatz structure?

You are asked to explain why copying an unknown quantum state to create backups is not generally possible. Which principle best supports this?

A circuit is intended to create a Bell state, but hardware results show unexpectedly low correlation even after basic readout mitigation. The circuit has many additional single-qubit gates inserted by transpilation. Which design change most directly helps preserve entanglement on noisy hardware?