3. Quantum Algorithms

Phaseestimation — Quiz

Test your understanding of phaseestimation with 5 practice questions.

Practice Questions

Question 1

In the HHL algorithm for solving linear systems, what is the primary role of the quantum phase estimation (QPE) subroutine?

Question 2

After performing phase estimation in the HHL algorithm, which controlled operation is applied to an ancilla qubit to achieve the matrix inversion?

Question 3

To achieve an energy precision $\delta E$ using QPE with $k$ ancilla qubits and a time-evolution operator $U=e^{-iHt}$, the evolution time $t$ must satisfy which condition?

Question 4

In standard QPE, to bound the phase estimation error by $\varepsilon$, the number of controlled-$U$ operations must scale as:

Question 5

Which hardware parameter most critically limits the achievable precision in quantum phase estimation on NISQ devices?