50 IBM A1000-088 - Assessment: Foundations of Quantum Computing Practice Questions: Question Bank 2025

A team is explaining why quantum computers can outperform classical computers on some tasks. Which statement best describes the role of superposition in quantum computing?

You prepare a qubit in the state |0> and apply a Hadamard (H) gate, then measure in the computational basis. What outcome should you expect over many repeated shots?

A developer wants to run a quantum circuit multiple times to estimate measurement probabilities (e.g., counts of bitstrings). In IBM Quantum tooling, which concept directly controls the number of repeated circuit executions?

A finance team is evaluating near-term quantum use cases. Which problem is most commonly framed as a candidate for quantum optimization methods in the NISQ era?

A student writes a circuit that ends with a measurement, then adds more gates after the measurement expecting them to affect the result. The output counts do not change as expected. What is the best explanation?

A circuit is intended to create a Bell state. Starting from |00>, which gate sequence correctly produces (|00> + |11>)/√2?

A user runs the same circuit on a simulator and on a real IBM Quantum device. The simulator results match theory, but the hardware results show additional bitstrings and skewed probabilities. What is the most likely cause?

A team is preparing circuits for execution on a specific IBM Quantum backend with limited qubit connectivity. Which practice best addresses connectivity constraints while keeping behavior consistent with the intended algorithm?

A researcher claims: "Because a quantum state is a vector, you can copy an unknown qubit state and distribute it to many places for parallel measurements." Which principle shows why this is not generally possible?

A developer is implementing Grover's search conceptually. For an unstructured search space of size N with a single marked item, what is the expected order of magnitude for the number of oracle iterations needed to maximize the probability of measuring the marked item?

A new team member claims that measuring a qubit in superposition will always return the same result if the circuit is re-run with the same inputs. Which statement best corrects this misunderstanding?

You want to create a Bell state starting from |00>. Which circuit accomplishes this?

In IBM Quantum workflows, what is the primary purpose of executing a circuit with many "shots"?

A researcher simulates a circuit and gets the expected probabilities. When running on real hardware, the counts differ noticeably. Which explanation best accounts for this difference?

You are designing a circuit intended to produce interference (e.g., in Deutsch-Jozsa-like patterns). Which practice is most important to enable interference effects?

A circuit produces correct results on a simulator, but on hardware it fails due to transpilation introducing additional SWAP operations. What is the most likely root cause?

A product team wants to identify where quantum computing may offer value in the near term. Which candidate problem is most realistic for NISQ-era exploration?

A team has a circuit with many repeated subcircuits and wants to reduce the runtime overhead when executing multiple variants. Which approach is a best practice on the IBM Quantum platform/tooling side?

A circuit prepares the two-qubit state (|00> + |11>)/√2. If you measure qubit 0 in the Z basis and obtain 0, what is the post-measurement state of qubit 1?

You build a circuit intended to implement a phase flip on |1> (i.e., apply a Z gate). After transpilation for a particular backend, you notice the circuit uses X-H-X-H instead of Z. Which statement best explains why this can still be correct?

A new team member says, "Because qubits can be in superposition, a quantum computer tries all answers at once and always gets the right one." What is the most accurate correction?

A developer wants to estimate the probability of measuring the state |11> from a 2-qubit circuit executed on IBM Quantum hardware. Which method is the most appropriate?

In IBM Quantum Composer, a learner builds a Bell-state circuit but observes outcomes spread across all four bitstrings instead of mostly 00 and 11. Which action is the best first troubleshooting step?

A circuit uses a Toffoli (CCX) gate, but the chosen IBM Quantum device does not natively support a 3-qubit gate. What is the expected behavior when submitting the job?

A team is experimenting with a small variational circuit and wants results that are more stable from run to run on real hardware. Which approach is the most appropriate best practice?

A circuit prepares |0> then applies H, then applies Z, then applies H again, and measures in the computational basis. What outcome distribution should be expected on an ideal simulator?

A researcher wants to compare an ideal circuit result to a noisy run that mimics a specific IBM Quantum backend's error characteristics, without consuming real device time. Which approach best fits this need?

A team is considering quantum computing for optimizing delivery routes. They are asked to justify why many near-term solutions are hybrid. What is the most accurate reason?

A student writes a circuit intending to create the entangled state (|00> + |11>)/sqrt(2), but the circuit is: apply H to qubit 0, then apply CNOT with qubit 1 as control and qubit 0 as target. On an ideal simulator, what state is produced?

You need to run a 6-qubit circuit on a real IBM Quantum device. The circuit includes two-qubit gates between qubits that are not directly connected on the chosen backend’s coupling map. What is the most likely consequence after compilation, and why does it matter?

A learner claims that a 2-qubit register can be fully described by listing the probability of each of the four basis states. What key piece of information is missing from that description in general?

A developer wants to ensure a measurement outcome is always 1 for a single qubit that starts in |0⟩. Which circuit accomplishes this?

In Qiskit, a user runs a circuit and receives a histogram of counts. What does the term "shots" represent in this context?

A business team asks for a near-term use case of quantum computing that is commonly explored on noisy devices today. Which option best fits current capabilities?

A student prepares the Bell state (|00⟩ + |11⟩)/√2 and measures both qubits in the computational basis. Which outcome pattern should they expect over many shots?

A developer uses a controlled-NOT (CX) gate with control qubit in |0⟩ and target in |1⟩. What is the resulting state after applying CX?

A user submits a job to an IBM Quantum backend and gets results that differ from the ideal simulator. They suspect noise. Which approach is generally recommended first to establish a baseline before applying advanced mitigation?

A team is choosing between a classical optimizer alone versus a hybrid quantum-classical approach for a small constrained optimization pilot on near-term hardware. Why is a hybrid approach commonly used in NISQ-era algorithms like VQE/QAOA?

A circuit creates an entangled state of two qubits. The developer then measures the first qubit but wants the second qubit to remain usable for further coherent operations. Which statement is most accurate?

A Qiskit circuit uses three qubits and includes CX gates between pairs that are not directly connected on the chosen hardware. When transpiled for that backend, the circuit depth increases significantly. What is the primary reason?

A learner is confused about why measuring a qubit changes what can be known about its state. Which statement best describes what a measurement does in the computational (Z) basis?

In IBM Quantum Composer, a user wants to create a Bell state from two qubits initially in |00⟩. Which gate sequence is the standard approach?

A team is unsure why running the same quantum circuit many times is necessary on real hardware. What is the primary reason to use many shots?

A developer writes a circuit intended to create entanglement, but the result histogram shows roughly 25% for each of 00, 01, 10, 11. Which is the most likely cause?

A researcher wants to verify that two qubits are entangled rather than merely correlated. Which method is most appropriate at a foundational level?

A student builds a circuit in Qiskit and notices that the transpiled circuit has more gates than the original. What is the most common reason for this increase?

A team is deciding whether to use a quantum approach for an optimization problem. Which statement best reflects a realistic near-term use case for quantum computing at a foundational level?

A developer observes that running the same circuit on an ideal simulator gives clean results, but running on real hardware produces significant unexpected outcomes. Which action is the best first step to diagnose whether noise is the main contributor?

You want to implement phase kickback in a simple oracle-style circuit. Which design choice enables a phase to be imprinted on a control qubit via a controlled operation?

A circuit outputs a state that is a superposition over several computational basis states. You need the probability of a specific bitstring with high confidence. Which approach best improves the statistical confidence without changing the algorithm’s logic?