qiskit.algorithms.PhaseEstimationResult

class PhaseEstimationResult(num_evaluation_qubits, circuit_result, phases)

Store and manipulate results from running PhaseEstimation.

This class is instantiated by the PhaseEstimation class, not via user code. The PhaseEstimation class generates a list of phases and corresponding weights. Upon completion it returns the results as an instance of this class. The main method for accessing the results is filter_phases.

The canonical phase satisfying the PhaseEstimator interface, returned by the attribute phase, is the most likely phase.

Parameters

• num_evaluation_qubits (int) – number of qubits in phase-readout register.

• circuit_result (Result) – result object returned by method running circuit.

• phases (Union[ndarray, Dict[str, float]]) – ndarray or dict of phases and frequencies determined by QPE.

__init__(num_evaluation_qubits, circuit_result, phases)

Parameters

• num_evaluation_qubits (int) – number of qubits in phase-readout register.

• circuit_result (Result) – result object returned by method running circuit.

• phases (Union[ndarray, Dict[str, float]]) – ndarray or dict of phases and frequencies determined by QPE.

Methods

__init__(num_evaluation_qubits, …)	type num_evaluation_qubits int
combine(result)	Any property from the argument that exists in the receiver is updated.
filter_phases([cutoff, as_float])	Return a filtered dict of phases (keys) and frequencies (values).

Attributes

circuit_result	Return the result object returned by running the QPE circuit (on hardware or simulator).
most_likely_phase	DEPRECATED - Return the most likely phase as a number in \([0.0, 1.0)\).
phase	Return the most likely phase as a number in \([0.0, 1.0)\).
phases	Return all phases and their frequencies computed by QPE.

property circuit_result

Return the result object returned by running the QPE circuit (on hardware or simulator).

This is useful for inspecting and troubleshooting the QPE algorithm.

Return type

Result

combine(result)

Any property from the argument that exists in the receiver is updated. :type result: AlgorithmResult :param result: Argument result with properties to be set.

Raises

TypeError – Argument is None

Return type

None

filter_phases(cutoff=0.0, as_float=True)

Return a filtered dict of phases (keys) and frequencies (values).

Only phases with frequencies (counts) larger than cutoff are included. It is assumed that the run method has been called so that the phases have been computed. When using a noiseless, shot-based simulator to read a single phase that can be represented exactly by num_evaluation_qubits, all the weight will be concentrated on a single phase. In all other cases, many, or all, bit strings will have non-zero weight. This method is useful for filtering out these uninteresting bit strings.

Parameters

• cutoff (float) – Minimum weight of number of counts required to keep a bit string. The default value is 0.0.

• as_float (bool) – If True, returned keys are floats in \([0.0, 1.0)\). If False returned keys are bit strings.

Return type

Dict

Returns

A filtered dict of phases (keys) and frequencies (values).

property most_likely_phase

DEPRECATED - Return the most likely phase as a number in \([0.0, 1.0)\).

1.0 corresponds to a phase of \(2\pi\). This selects the phase corresponding to the bit string with the highesest probability. This is the most likely phase.

Return type

float

property phase

Return the most likely phase as a number in \([0.0, 1.0)\).

1.0 corresponds to a phase of \(2\pi\). This selects the phase corresponding to the bit string with the highesest probability. This is the most likely phase.

Return type

float

property phases

Return all phases and their frequencies computed by QPE.

This is an array or dict whose values correspond to weights on bit strings.

Return type

Union[ndarray, dict]