# Copyright 2019 1QBit
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Performs energy estimations for a molecule with a parametric circuit.
Performs energy estimations for a given molecule and a choice of ansatz
circuit that is supported by the hardware. A concrete class will contain a
nested Enum class that exposes the supported ansatze to the users. The state
of the class is created in the costructor so that the `simulate` function
can just accept an amplitude array and return an energy.
amplitude_dimension (int): The size of the amplitudes list that should
be provided to the solver.
initial_wavefunction (numpy.array): The initial wavefuntion for the
n_qubits (int): The number of qubits in the circuit.
def __init__(self, molecule, anstatz, mean_field=None, backend_options=None):
self.initial_wavefunction = None
self.n_qubits = None
self.amplitude_dimension = None
def simulate(self, amplitudes):
"""Performs an energy simulation for the given amplitudes.
amplitudes (list): The amplitudes to use in the simulation.
float: The energy from the simulation.
ValueError: If len(amplitudes) doesn't equal amplitude_dimension.
""" Returns the RDM from the simulation.
This is intended to be called after the simulation loop of the calling
code has converged to be passed on to problem decompositions. In a
concrete implementation, the `simulate` function would set the necessary
internal state for the class so that this function can return the
reduced density matrix.
(numpy.array, numpy.array): The one- and two-element RDMs (float64).
RuntimeError: If no simulation has been run.
"""Returns reasonably good initial parameters for a VQE simulation.
The construction of the object should set the state so that this function
can produce its output.