qiskit_nature.second_q.circuit.library.ansatzes.chc のソースコード

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# (C) Copyright IBM 2020, 2023.
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""" Compact Heuristic ansatz for vibrational Chemistry """

from __future__ import annotations

from typing import Any

import numpy as np

from qiskit import QuantumRegister, QuantumCircuit
from qiskit.circuit.library import BlueprintCircuit

from qiskit.circuit import ParameterVector


[ドキュメント]class CHC(BlueprintCircuit): """This trial wavefunction is the Compact Heuristic for vibrational Chemistry. The trial wavefunction is as defined in Ollitrault Pauline J., Chemical science 11 (2020): 6842-6855. It aims at approximating the UCC Ansatz for a lower CNOT count. Note: It is not particle number conserving and the accuracy of the approximation decreases with the number of excitations. """ def __init__( self, num_qubits: int | None = None, excitations: list[tuple[tuple[Any, ...], ...]] | None = None, *, reps: int = 1, ladder: bool = False, initial_state: QuantumCircuit | None = None, ) -> None: """ Args: num_qubits: The number of qubits. excitations: The list of excitations encoded as tuples of tuples. Each tuple in the list is a pair of tuples. The first tuple contains the occupied spin orbital indices whereas the second one contains the indices of the unoccupied spin orbitals. reps: The number of repetitions of basic module. ladder: Boolean flag whether or not to use ladder of CNOTs between to indices in the entangling block. initial_state: An initial state to prepend to the ansatz. """ super().__init__() self._reps = reps self._bounds = None self._ladder = ladder self._num_qubits = None self._excitations = None self._initial_state = None self._num_parameters = None self._support_parameterized_circuit = True if num_qubits is not None: self.num_qubits = num_qubits if excitations is not None: self.excitations = excitations if initial_state is not None: self.initial_state = initial_state @property def num_qubits(self) -> int | None: """Number of qubits of the ansatz. Returns: int: An integer indicating the number of qubits. """ return self._num_qubits @num_qubits.setter def num_qubits(self, num_qubits: int) -> None: """Set the number of qubits of the ansatz. Args: num_qubits: An integer indicating the number of qubits. """ if self._num_qubits != num_qubits: # invalidate the circuit self._invalidate() self._num_qubits = num_qubits self.qregs = [QuantumRegister(num_qubits, name="q")] @property def excitations(self) -> list[tuple[tuple[Any, ...], ...]] | None: """The excitation indices to be included in the circuit.""" return self._excitations @excitations.setter def excitations(self, excitations: list[tuple[tuple[Any, ...], ...]]) -> None: """Sets the excitation indices to be included in the circuit.""" self._invalidate() self._excitations = excitations self._num_parameters = len(excitations) * self._reps self._bounds = [(-np.pi, np.pi)] * self._num_parameters @property def initial_state(self) -> QuantumCircuit | None: """The initial state.""" return self._initial_state @initial_state.setter def initial_state(self, initial_state: QuantumCircuit) -> None: """Sets the initial state.""" self._invalidate() self._initial_state = initial_state def _check_configuration(self, raise_on_failure: bool = True) -> bool: """Check if the configuration of the CHC class is valid. Args: raise_on_failure: Whether to raise on failure. Returns: True, if the configuration is valid and the circuit can be constructed. Otherwise an ValueError is raised. Raises: ValueError: If the number of qubits is not specified. ValueError: If the number of parameters is not specified. ValueError: If the excitation list is not specified. """ error_msg = "The %s is None but must be set before the circuit can be built." if self._num_qubits is None: if raise_on_failure: raise ValueError(error_msg, "number of qubits") return False if self._num_parameters is None: if raise_on_failure: raise ValueError(error_msg, "number of parameters") return False if self._excitations is None: if raise_on_failure: raise ValueError(error_msg, "excitation list") return False return True def _build(self) -> None: """ Construct the ansatz, given its parameters. Returns: QuantumCircuit: a quantum circuit with given `parameters` Raises: ValueError: only supports single and double excitations at the moment. """ if self._is_built: return super()._build() self.data.clear() parameters = ParameterVector("θ", self._num_parameters) q = self.qubits if isinstance(self._initial_state, QuantumCircuit): self.append(self._initial_state.to_gate(), range(self._initial_state.num_qubits)) count = 0 for _ in range(self._reps): for exc in self.excitations: occ, unocc = exc if len(occ) == 1: i = occ[0] r = unocc[0] self.p(-parameters[count] / 4 + np.pi / 4, q[i]) self.p(-parameters[count] / 4 - np.pi / 4, q[r]) self.h(q[i]) self.h(q[r]) if self._ladder: for qubit in range(i, r): self.cx(q[qubit], q[qubit + 1]) else: self.cx(q[i], q[r]) self.p(parameters[count], q[r]) if self._ladder: for qubit in range(r, i, -1): self.cx(q[qubit - 1], q[qubit]) else: self.cx(q[i], q[r]) self.h(q[i]) self.h(q[r]) self.p(-parameters[count] / 4 - np.pi / 4, q[i]) self.p(-parameters[count] / 4 + np.pi / 4, q[r]) elif len(occ) == 2: i = occ[0] r = unocc[0] j = occ[1] s = unocc[1] # pylint: disable=invalid-name self.sdg(q[r]) self.h(q[i]) self.h(q[r]) self.h(q[j]) self.h(q[s]) if self._ladder: for qubit in range(i, r): self.cx(q[qubit], q[qubit + 1]) self.barrier(q[qubit], q[qubit + 1]) else: self.cx(q[i], q[r]) self.cx(q[r], q[j]) if self._ladder: for qubit in range(j, s): self.cx(q[qubit], q[qubit + 1]) self.barrier(q[qubit], q[qubit + 1]) else: self.cx(q[j], q[s]) self.p(parameters[count], q[s]) if self._ladder: for qubit in range(s, j, -1): self.cx(q[qubit - 1], q[qubit]) self.barrier(q[qubit - 1], q[qubit]) else: self.cx(q[j], q[s]) self.cx(q[r], q[j]) if self._ladder: for qubit in range(r, i, -1): self.cx(q[qubit - 1], q[qubit]) self.barrier(q[qubit - 1], q[qubit]) else: self.cx(q[i], q[r]) self.h(q[i]) self.h(q[r]) self.h(q[j]) self.h(q[s]) self.p(-parameters[count] / 2 + np.pi / 2, q[i]) self.p(-parameters[count] / 2 + np.pi, q[r]) else: raise ValueError( "Limited to single and double excitations, " "higher order is not implemented" ) count += 1