""":class:`~mpqp.core.instruction.measurement.measure.Measure` is the
base class for measurements. It regroups all the attributes and methods
common to all types of measurements we support.
A measurement can be of two types:
:class:`~mpqp.core.instruction.measurement.basis_measure.BasisMeasure`
or
:class:`~mpqp.core.instruction.measurement.expectation_value.ExpectationMeasure`,
described in details bellow."""
from __future__ import annotations
from abc import ABC
from typing import Optional
from mpqp.core.instruction import Instruction
from mpqp.core.instruction.gates import Gate
[docs]
class Measure(Instruction, ABC):
"""Abstract class representing the measurement of the quantum state
generated by a quantum circuit.
This class is used to regroup attributes and methods shared by all different
types of measures.
We distinguish two types of measures:
- Basis measurement (measure some qubits in a specific basis, sample
mode, or retrieve the StateVector when shots is equal to zero)
- Expectation value (use of an observable, exact or sample mode)
Args:
targets: List of indices referring to the qubits on which the measure
will be applied.
shots: Number of times the circuit should be run, each of these times is
called a shot.
label: Label used to identify the measure.
"""
def __init__(
self,
targets: Optional[list[int]] = None,
shots: int = 0,
label: Optional[str] = None,
):
if shots < 0:
raise ValueError(f"Negative number of shot makes no sense, given {shots}")
if targets is None:
targets = []
super().__init__(targets, label)
self.shots = shots
"""See parameter description."""
self.label = label
"""See parameter description."""
self._dynamic = False
if len(targets) == 0:
self._dynamic = True
@property
def pre_measure(self) -> list[Gate]:
"""Operations needed so that the only measurement needed at the end of
the circuit is a standard measurement in the computational basis with
the qubits in ascending order. This list of operations can for instance
include swap gates and U3 gates."""
return []