About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
phase_estimation
class qiskit.circuit.library.phase_estimation(num_evaluation_qubits, unitary, name='QPE')
Bases:
Phase Estimation circuit.
In the Quantum Phase Estimation (QPE) algorithm [1, 2, 3], the Phase Estimation circuit is used to estimate the phase of an eigenvalue of a unitary operator , provided with the corresponding eigenstate . That is
This estimation (and thereby this circuit) is a central routine to several well-known algorithms, such as Shor’s algorithm or Quantum Amplitude Estimation.
Parameters
- num_evaluation_qubits (int) – The number of evaluation qubits.
- unitary (QuantumCircuit) – The unitary operation which will be repeated and controlled.
- name (str) – The name of the circuit.
Return type
Reference Circuit:
from qiskit.circuit import QuantumCircuit
from qiskit.circuit.library import phase_estimation
unitary = QuantumCircuit(2)
unitary.x(0)
unitary.y(1)
circuit = phase_estimation(3, unitary)
circuit.draw('mpl')

References:
[1]: Kitaev, A. Y. (1995). Quantum measurements and the Abelian Stabilizer Problem. 1–22.
[2]: Michael A. Nielsen and Isaac L. Chuang. 2011.
Quantum Computation and Quantum Information: 10th Anniversary Edition (10th ed.). Cambridge University Press, New York, NY, USA.
[3]: Qiskit
Was this page helpful?
Report a bug or request content on GitHub.