Source code for qiskit.opflow.primitive_ops.primitive_op

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# (C) Copyright IBM 2020, 2023.
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
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"""PrimitiveOp Class"""

from typing import Dict, List, Optional, Set, Union, cast

import numpy as np
import scipy.linalg
from scipy.sparse import spmatrix

from qiskit import QuantumCircuit
from qiskit.circuit import Instruction, ParameterExpression
from qiskit.opflow.operator_base import OperatorBase
from qiskit.quantum_info import Operator, Pauli, SparsePauliOp, Statevector
from qiskit.utils.deprecation import deprecate_func

[docs]class PrimitiveOp(OperatorBase): r""" Deprecated: A class for representing basic Operators, backed by Operator primitives from Terra. This class (and inheritors) primarily serves to allow the underlying primitives to "flow" - i.e. interoperability and adherence to the Operator formalism - while the core computational logic mostly remains in the underlying primitives. For example, we would not produce an interface in Terra in which ``QuantumCircuit1 + QuantumCircuit2`` equaled the Operator sum of the circuit unitaries, rather than simply appending the circuits. However, within the Operator flow summing the unitaries is the expected behavior. Note that all mathematical methods are not in-place, meaning that they return a new object, but the underlying primitives are not copied. """ def __init_subclass__(cls): cls.__new__ = lambda cls, *args, **kwargs: super().__new__(cls) @staticmethod # pylint: disable=unused-argument def __new__( cls, primitive: Union[ Instruction, QuantumCircuit, List, np.ndarray, spmatrix, Operator, Pauli, SparsePauliOp ], coeff: Union[complex, ParameterExpression] = 1.0, ) -> "PrimitiveOp": """A factory method to produce the correct type of PrimitiveOp subclass based on the primitive passed in. Primitive and coeff arguments are passed into subclass's init() as-is automatically by new(). Args: primitive: The operator primitive being wrapped. coeff: A coefficient multiplying the primitive. Returns: The appropriate PrimitiveOp subclass for ``primitive``. Raises: TypeError: Unsupported primitive type passed. """ # pylint: disable=cyclic-import if isinstance(primitive, (Instruction, QuantumCircuit)): from .circuit_op import CircuitOp return super().__new__(CircuitOp) if isinstance(primitive, (list, np.ndarray, spmatrix, Operator)): from .matrix_op import MatrixOp return super().__new__(MatrixOp) if isinstance(primitive, Pauli): from .pauli_op import PauliOp return super().__new__(PauliOp) if isinstance(primitive, SparsePauliOp): from .pauli_sum_op import PauliSumOp return super().__new__(PauliSumOp) raise TypeError( "Unsupported primitive type {} passed into PrimitiveOp " "factory constructor".format(type(primitive)) ) @deprecate_func( since="0.24.0", additional_msg="For code migration guidelines, visit", ) def __init__( self, primitive: Union[QuantumCircuit, Operator, Pauli, SparsePauliOp, OperatorBase], coeff: Union[complex, ParameterExpression] = 1.0, ) -> None: """ Args: primitive: The operator primitive being wrapped. coeff: A coefficient multiplying the primitive. """ super().__init__() self._primitive = primitive self._coeff = coeff @property def primitive(self) -> Union[QuantumCircuit, Operator, Pauli, SparsePauliOp, OperatorBase]: """The primitive defining the underlying function of the Operator. Returns: The primitive object. """ return self._primitive @property def coeff(self) -> Union[complex, ParameterExpression]: """ The scalar coefficient multiplying the Operator. Returns: The coefficient. """ return self._coeff @property def num_qubits(self) -> int: raise NotImplementedError @property def settings(self) -> Dict: """Return operator settings.""" return {"primitive": self._primitive, "coeff": self._coeff}
[docs] def primitive_strings(self) -> Set[str]: raise NotImplementedError
[docs] def add(self, other: OperatorBase) -> OperatorBase: raise NotImplementedError
[docs] def adjoint(self) -> OperatorBase: raise NotImplementedError
[docs] def equals(self, other: OperatorBase) -> bool: raise NotImplementedError
[docs] def mul(self, scalar: Union[complex, ParameterExpression]) -> OperatorBase: if not isinstance(scalar, (int, float, complex, ParameterExpression)): raise ValueError( "Operators can only be scalar multiplied by float or complex, not " "{} of type {}.".format(scalar, type(scalar)) ) # Need to return self.__class__ in case the object is one of the inherited OpPrimitives return self.__class__(self.primitive, coeff=self.coeff * scalar)
[docs] def tensor(self, other: OperatorBase) -> OperatorBase: raise NotImplementedError
[docs] def tensorpower(self, other: int) -> Union[OperatorBase, int]: # Hack to make Z^(I^0) work as intended. if other == 0: return 1 if not isinstance(other, int) or other < 0: raise TypeError("Tensorpower can only take positive int arguments") temp = PrimitiveOp(self.primitive, coeff=self.coeff) # type: OperatorBase for _ in range(other - 1): temp = temp.tensor(self) return temp
[docs] def compose( self, other: OperatorBase, permutation: Optional[List[int]] = None, front: bool = False ) -> OperatorBase: # pylint: disable=cyclic-import from ..list_ops.composed_op import ComposedOp new_self, other = self._expand_shorter_operator_and_permute(other, permutation) if isinstance(other, ComposedOp): comp_with_first = new_self.compose(other.oplist[0]) if not isinstance(comp_with_first, ComposedOp): new_oplist = [comp_with_first] + other.oplist[1:] return ComposedOp(new_oplist, coeff=other.coeff) return ComposedOp([new_self] + other.oplist, coeff=other.coeff) return ComposedOp([new_self, other])
def _expand_dim(self, num_qubits: int) -> OperatorBase: raise NotImplementedError
[docs] def permute(self, permutation: List[int]) -> OperatorBase: raise NotImplementedError
[docs] def exp_i(self) -> OperatorBase: """Return Operator exponentiation, equaling e^(-i * op)""" # pylint: disable=cyclic-import from ..evolutions.evolved_op import EvolvedOp return EvolvedOp(self)
[docs] def log_i(self, massive: bool = False) -> OperatorBase: """Return a ``MatrixOp`` equivalent to log(H)/-i for this operator H. This function is the effective inverse of exp_i, equivalent to finding the Hermitian Operator which produces self when exponentiated.""" # pylint: disable=cyclic-import from ..operator_globals import EVAL_SIG_DIGITS from .matrix_op import MatrixOp return MatrixOp( np.around( scipy.linalg.logm(self.to_matrix(massive=massive)) / -1j, decimals=EVAL_SIG_DIGITS ) )
def __str__(self) -> str: raise NotImplementedError def __repr__(self) -> str: return f"{type(self).__name__}({repr(self.primitive)}, coeff={self.coeff})"
[docs] def eval( self, front: Optional[ Union[str, Dict[str, complex], np.ndarray, OperatorBase, Statevector] ] = None, ) -> Union[OperatorBase, complex]: raise NotImplementedError
@property def parameters(self): params = set() if isinstance(self.primitive, (OperatorBase, QuantumCircuit)): params.update(self.primitive.parameters) if isinstance(self.coeff, ParameterExpression): params.update(self.coeff.parameters) return params
[docs] def assign_parameters(self, param_dict: dict) -> OperatorBase: param_value = self.coeff if isinstance(self.coeff, ParameterExpression): unrolled_dict = self._unroll_param_dict(param_dict) if isinstance(unrolled_dict, list): # pylint: disable=cyclic-import from ..list_ops.list_op import ListOp return ListOp([self.assign_parameters(param_dict) for param_dict in unrolled_dict]) if self.coeff.parameters <= set(unrolled_dict.keys()): binds = {param: unrolled_dict[param] for param in self.coeff.parameters} param_value = complex(self.coeff.bind(binds)) if abs(param_value.imag) == 0: param_value = param_value.real return self.__class__(self.primitive, coeff=param_value)
# Nothing to collapse here.
[docs] def reduce(self) -> OperatorBase: return self
[docs] def to_matrix(self, massive: bool = False) -> np.ndarray: raise NotImplementedError
[docs] def to_matrix_op(self, massive: bool = False) -> OperatorBase: """Returns a ``MatrixOp`` equivalent to this Operator.""" coeff = self.coeff op = self.copy() op._coeff = 1 prim_mat = op.to_matrix(massive=massive) from .matrix_op import MatrixOp return MatrixOp(prim_mat, coeff=coeff)
[docs] def to_instruction(self) -> Instruction: """Returns an ``Instruction`` equivalent to this Operator.""" raise NotImplementedError
[docs] def to_circuit(self) -> QuantumCircuit: """Returns a ``QuantumCircuit`` equivalent to this Operator.""" qc = QuantumCircuit(self.num_qubits) qc.append(self.to_instruction(), qargs=range(self.primitive.num_qubits)) return qc.decompose()
[docs] def to_circuit_op(self) -> OperatorBase: """Returns a ``CircuitOp`` equivalent to this Operator.""" from .circuit_op import CircuitOp if self.coeff == 0: return CircuitOp(QuantumCircuit(self.num_qubits), coeff=0) return CircuitOp(self.to_circuit(), coeff=self.coeff)
[docs] def to_pauli_op(self, massive: bool = False) -> OperatorBase: """Returns a sum of ``PauliOp`` s equivalent to this Operator.""" # pylint: disable=cyclic-import from .matrix_op import MatrixOp mat_op = cast(MatrixOp, self.to_matrix_op(massive=massive)) sparse_pauli = SparsePauliOp.from_operator(mat_op.primitive) if not sparse_pauli.to_list(): from ..operator_globals import I return (I ^ self.num_qubits) * 0.0 from .pauli_op import PauliOp if len(sparse_pauli) == 1: label, coeff = sparse_pauli.to_list()[0] coeff = coeff.real if np.isreal(coeff) else coeff return PauliOp(Pauli(label), coeff * self.coeff) from ..list_ops.summed_op import SummedOp return SummedOp( [ PrimitiveOp( Pauli(label), coeff.real if coeff == coeff.real else coeff, ) for (label, coeff) in sparse_pauli.to_list() ], self.coeff, )