What does Quantum Phase Estimation estimate?

Question: In Quantum Phase Estimation, what quantity is being estimated? A) The number of gates in a quantum circuit B) The exact measurement count of every bitstring C) The eigenphase θ where U|ψ⟩ = e^(2πiθ)|ψ⟩ D) The coupling map of the backend Correct: C Explanation: Quantum Phase Estimation estimates the phase θ associated with an eigenvalue of a unitary operator U. If |ψ⟩ is an eigenstate of U, the algorithm extracts information about the phase in e^(2πiθ). Topic: quantum computing / QPE / eigenvalues