IBM A1000-112: Assessment: Fundamentals of Quantum Computation Using Qiskit v0.2x Developer Advanced Practice Exam: Hard Questions 2025

You are implementing a quantum circuit that requires measuring a subset of qubits mid-circuit while preserving quantum coherence in unmeasured qubits for subsequent operations. After measurement, you need to apply conditional operations based on classical bit outcomes. Which Qiskit v0.2x approach correctly implements this while maintaining compatibility with both simulators and real quantum hardware?

When implementing Grover's algorithm for a 4-qubit search space with multiple marked states, you observe that after the optimal number of iterations, the measurement probability for marked states is only 65% instead of the expected ~95%. What is the MOST likely cause of this degradation?

You are optimizing a VQE (Variational Quantum Eigensolver) implementation for finding the ground state energy of a molecular Hamiltonian. The ansatz circuit depth is 50 gates, and convergence is slow with high shot noise. Which combination of strategies would MOST effectively improve both convergence speed and accuracy?

In Qiskit v0.2x, you need to transpile a circuit for execution on a quantum backend with limited connectivity. The original circuit has CNOT gates between non-adjacent qubits. After transpilation with optimization_level=3, you notice the circuit depth increased by 400% and gate count tripled. What is the BEST approach to mitigate this while maintaining logical equivalence?

You are simulating a 12-qubit quantum circuit using different Qiskit simulators. The circuit includes noise modeling with depolarizing errors (p=0.001) and thermal relaxation (T1=50μs, T2=70μs). Memory consumption exceeds available RAM with StatevectorSimulator. Which simulator configuration would provide the MOST accurate results while being computationally feasible?

When implementing quantum phase estimation (QPE) for a unitary operator U with an unknown eigenvalue, you use 8 counting qubits for phase precision. After multiple runs, you consistently measure the bit string '10100000' in the counting register. What is the estimated phase θ (where the eigenvalue is e^(2πiθ)) and what limitation should you be aware of?

You are debugging a Qiskit circuit that implements a quantum Fourier transform (QFT) on 5 qubits. The circuit executes without errors, but the output distribution shows unexpected peaks. Upon inspection, you realize you forgot to apply the SWAP gates at the end to reverse qubit order. How does this affect the interpretation of measurement results?

When executing circuits on IBM quantum hardware via Qiskit Runtime, you need to balance between queue time, circuit execution time, and job cost. You have 500 circuits with varying depths (50-200 gates) to execute for a variational algorithm. What job submission strategy provides the BEST tradeoff?

You are implementing a custom quantum gate decomposition in Qiskit v0.2x. The gate is a controlled-rotation Ry(θ) that needs to be decomposed into the basis gates {Rz, Sx, X, CNOT}. The decomposition must be optimal (minimal gate count) and preserve the controlled nature. Which approach correctly achieves this?

In a quantum error mitigation study, you implement zero-noise extrapolation (ZNE) by scaling noise through gate stretching. You run circuits at noise scale factors [1.0, 1.5, 2.0, 2.5] and fit the results. The expectation values are [0.45, 0.38, 0.32, 0.25]. Using linear extrapolation to zero noise, what is the mitigated estimate, and what is a critical limitation of this approach?