Replace the InitialState components by circuits

README.md

@@ -223,12 +223,15 @@ from qiskit.aqua.components.optimizers import L_BFGS_B
 optimizer = L_BFGS_B()
 
 # setup the initial state for the variational form
-from qiskit.chemistry.components.initial_states import HartreeFock
+from qiskit.chemistry.circuit.library import HartreeFock
 init_state = HartreeFock(num_spin_orbitals, num_particles)
 
 # setup the variational form for VQE
 from qiskit.circuit.library import TwoLocal
-var_form = TwoLocal(num_qubits, ['ry', 'rz'], 'cz', initial_state=init_state)
+var_form = TwoLocal(num_qubits, ['ry', 'rz'], 'cz')
+
+# add the initial state
+var_form.compose(init_state, front=True)
 
 # setup and run VQE
 from qiskit.aqua.algorithms import VQE

qiskit/aqua/algorithms/education/eoh.py

@@ -16,7 +16,7 @@
 import logging
 
 from typing import Optional, Union, Dict, Any
-from qiskit import QuantumRegister
+from qiskit import QuantumRegister, QuantumCircuit
 from qiskit.providers import BaseBackend
 from qiskit.providers import Backend
 from qiskit.aqua import QuantumInstance
@@ -42,7 +42,7 @@ class EOH(QuantumAlgorithm):
     """
 
     def __init__(self, operator: LegacyBaseOperator,
-                 initial_state: InitialState,
+                 initial_state: Union[InitialState, QuantumCircuit],
                  evo_operator: LegacyBaseOperator,
                  evo_time: float = 1,
                  num_time_slices: int = 1,
@@ -84,7 +84,11 @@ def construct_circuit(self):
             QuantumCircuit: the circuit.
         """
         quantum_registers = QuantumRegister(self._operator.num_qubits, name='q')
-        qc = self._initial_state.construct_circuit('circuit', quantum_registers)
+        if isinstance(self._initial_state, QuantumCircuit):
+            qc = QuantumCircuit(quantum_registers)
+            qc.compose(self._initial_state, inplace=True)
+        else:
+            qc = self._initial_state.construct_circuit('circuit', quantum_registers)
 
         qc += self._evo_operator.evolve(
             evo_time=self._evo_time,

qiskit/aqua/algorithms/linear_solvers/hhl.py

@@ -91,7 +91,7 @@ def __init__(
             truncate_powerdim: bool = False,
             truncate_hermitian: bool = False,
             eigs: Optional[Eigenvalues] = None,
-            init_state: Optional[InitialState] = None,
+            init_state: Optional[Union[QuantumCircuit, InitialState]] = None,
             reciprocal: Optional[Reciprocal] = None,
             num_q: int = 0,
             num_a: int = 0,
@@ -206,7 +206,10 @@ def construct_circuit(self, measurement: bool = False) -> QuantumCircuit:
         qc = QuantumCircuit(q)
 
         # InitialState
-        qc += self._init_state.construct_circuit("circuit", q)
+        if isinstance(self._init_state, QuantumCircuit):
+            qc.compose(self._init_state, inplace=True)
+        elif self._init_state is not None:
+            qc += self._init_state.construct_circuit("circuit", q)
 
         # EigenvalueEstimation (QPE)
         qc += self._eigs.construct_circuit("circuit", q)

qiskit/aqua/algorithms/minimum_eigen_solvers/iqpe.py

@@ -57,7 +57,7 @@ class IQPE(QuantumAlgorithm, MinimumEigensolver):
 
     def __init__(self,
                  operator: Optional[Union[OperatorBase, LegacyBaseOperator]] = None,
-                 state_in: Optional[InitialState] = None,
+                 state_in: Optional[Union[QuantumCircuit, InitialState]] = None,
                  num_time_slices: int = 1,
                  num_iterations: int = 1,
                  expansion_mode: str = 'suzuki',
@@ -192,7 +192,10 @@ def construct_circuit(self,
         self._ancillary_register = a
         self._state_register = q
         qc = QuantumCircuit(q)
-        qc += self._state_in.construct_circuit('circuit', q)
+        if isinstance(self._state_in, QuantumCircuit):
+            qc.append(self._state_in, q)
+        else:
+            qc += self._state_in.construct_circuit('circuit', q)
         # hadamard on a[0]
         qc.add_register(a)
         qc.h(a[0])

qiskit/aqua/algorithms/minimum_eigen_solvers/qaoa/qaoa.py

@@ -16,6 +16,7 @@
 import logging
 import numpy as np
 
+from qiskit.circuit import QuantumCircuit
 from qiskit.providers import BaseBackend
 from qiskit.providers import Backend
 from qiskit.aqua import QuantumInstance
@@ -67,7 +68,7 @@ def __init__(self,
                  operator: Union[OperatorBase, LegacyBaseOperator] = None,
                  optimizer: Optimizer = None,
                  p: int = 1,
-                 initial_state: Optional[InitialState] = None,
+                 initial_state: Optional[Union[QuantumCircuit, InitialState]] = None,
                  mixer: Union[OperatorBase, LegacyBaseOperator] = None,
                  initial_point: Optional[np.ndarray] = None,
                  gradient: Optional[Union[GradientBase, Callable[[Union[np.ndarray, List]],

qiskit/aqua/algorithms/minimum_eigen_solvers/qaoa/var_form.py

@@ -12,10 +12,11 @@
 
 """Global X phases and parameterized problem hamiltonian."""
 
-from typing import Optional
+from typing import Optional, Union
 
 import numpy as np
 
+from qiskit import QuantumCircuit
 from qiskit.aqua.operators import (OperatorBase, X, I, H, CircuitStateFn,
                                    EvolutionFactory, LegacyBaseOperator)
 from qiskit.aqua.components.variational_forms import VariationalForm
@@ -31,7 +32,7 @@ class QAOAVarForm(VariationalForm):
     def __init__(self,
                  cost_operator: OperatorBase,
                  p: int,
-                 initial_state: Optional[InitialState] = None,
+                 initial_state: Optional[Union[QuantumCircuit, InitialState]] = None,
                  mixer_operator: Optional[OperatorBase] = None):
         """
         Constructor, following the QAOA paper https://arxiv.org/abs/1411.4028
@@ -81,9 +82,10 @@ def construct_circuit(self, parameters, q=None):
             ))
 
         # initialize circuit, possibly based on given register/initial state
-        if self._initial_state is not None:
-            stateVector = CircuitStateFn(self._initial_state.construct_circuit('circuit'))
-            circuit = stateVector.to_circuit_op()
+        if isinstance(self._initial_state, QuantumCircuit):
+            circuit = CircuitStateFn(self._initial_state)
+        elif self._initial_state is not None:
+            circuit = CircuitStateFn(self._initial_state.construct_circuit('circuit'))
         else:
             circuit = (H ^ self._num_qubits)
 

qiskit/aqua/algorithms/minimum_eigen_solvers/qpe.py

@@ -56,7 +56,7 @@ class QPE(QuantumAlgorithm, MinimumEigensolver):
 
     def __init__(self,
                  operator: Optional[Union[OperatorBase, LegacyBaseOperator]] = None,
-                 state_in: Optional[InitialState] = None,
+                 state_in: Optional[Union[InitialState, QuantumCircuit]] = None,
                  iqft: Optional[QuantumCircuit] = None,
                  num_time_slices: int = 1,
                  num_ancillae: int = 1,

qiskit/aqua/circuits/phase_estimation_circuit.py

@@ -12,7 +12,7 @@
 
 """Quantum Phase Estimation Circuit."""
 
-from typing import Optional, List
+from typing import Optional, List, Union
 import numpy as np
 
 from qiskit import QuantumRegister, QuantumCircuit, ClassicalRegister
@@ -33,7 +33,7 @@ class PhaseEstimationCircuit:
     def __init__(
             self,
             operator: Optional[WeightedPauliOperator] = None,
-            state_in: Optional[InitialState] = None,
+            state_in: Optional[Union[QuantumCircuit, InitialState]] = None,
             iqft: Optional[QuantumCircuit] = None,
             num_time_slices: int = 1,
             num_ancillae: int = 1,
@@ -48,7 +48,7 @@ def __init__(
         """
         Args:
             operator: the hamiltonian Operator object
-            state_in: the InitialState component
+            state_in: the InitialState component or a quantum circuit
             representing the initial quantum state
             iqft: the Inverse Quantum Fourier Transform as circuit or
                 Aqua component
@@ -158,7 +158,9 @@ def construct_circuit(
                 qc.add_register(aux)
 
             # initialize state_in
-            if self._state_in is not None:
+            if isinstance(self._state_in, QuantumCircuit):
+                qc.append(self._state_in.to_gate(), q)
+            elif isinstance(self._state_in, InitialState):
                 qc.data += self._state_in.construct_circuit('circuit', q).data
             elif self._state_in_circuit_factory is not None:
                 self._state_in_circuit_factory.build(qc, q, aux)

qiskit/aqua/components/initial_states/custom.py

@@ -112,6 +112,11 @@ def __init__(self,
                 self._state_vector = normalize_vector(state_vector)
                 self._state = None
 
+    @staticmethod
+    def _replacement():
+        return 'Custom(state_vector=vector) is the same as a circuit where the ' \
+                + '``initialize(vector/np.linalg.norm(vector))`` method has been called.'
+
     def construct_circuit(self, mode='circuit', register=None):
         # pylint: disable=import-outside-toplevel
         from qiskit import BasicAer

qiskit/aqua/components/initial_states/initial_state.py

@@ -15,6 +15,7 @@
 form or in eoh as a trial state to evolve
 """
 
+import warnings
 from typing import Optional
 # below to allow it for python 3.6.1
 try:
@@ -39,6 +40,17 @@ class InitialState(ABC):
     def __init__(self) -> None:
         super().__init__()
 
+        warnings.warn('The {} class is deprecated as of Aqua 0.9 and will be removed no earlier '
+                      'than 3 months after the release date. Instead, all algorithms and circuits '
+                      'accept a plain QuantumCircuit. {}'.format(
+                          self.__class__.__name__, self._replacement(),
+                      ),
+                      category=DeprecationWarning, stacklevel=2)
+
+    @staticmethod
+    def _replacement():
+        return ''
+
     @abstractmethod
     def construct_circuit(self,
                           mode: str = 'circuit',

qiskit/aqua/components/initial_states/var_form_based.py

@@ -13,6 +13,7 @@
 """The variational form based initial state"""
 
 from typing import Union, List, Dict
+import warnings
 import numpy as np
 from qiskit import QuantumCircuit
 from qiskit.circuit import Parameter
@@ -51,6 +52,13 @@ def __init__(self,
         self._var_form = var_form
         self._var_form_params = params
 
+        warnings.warn('The {} class is deprecated as of Aqua 0.9 and will be removed no earlier '
+                      'than 3 months after the release date. Instead, all algorithms and circuits '
+                      'accept a plain QuantumCircuit.'.format(
+                          self.__class__.__name__
+                      ),
+                      category=DeprecationWarning, stacklevel=2)
+
     def construct_circuit(self, mode='circuit', register=None):
         """
         Construct the statevector of desired initial state.

qiskit/aqua/components/initial_states/zero.py

@@ -37,6 +37,10 @@ def __init__(self, num_qubits: int) -> None:
         validate_min('num_qubits', num_qubits, 1)
         self._num_qubits = num_qubits
 
+    @staticmethod
+    def _replacement():
+        return 'Zero(num_qubits) is the same as a empty QuantumCircuit(num_qubits).'
+
     def construct_circuit(self, mode='circuit', register=None):
         if mode == 'vector':
             return np.array([1.0] + [0.0] * (np.power(2, self._num_qubits) - 1))

qiskit/aqua/operators/legacy/weighted_pauli_operator.py

@@ -1250,7 +1250,7 @@ def two_qubit_reduction(operator, num_particles):
                         "Return the empty operator back.")
             return operator
 
-        if isinstance(num_particles, list):
+        if isinstance(num_particles, (tuple, list)):
             num_alpha = num_particles[0]
             num_beta = num_particles[1]
         else:

qiskit/chemistry/algorithms/ground_state_solvers/minimum_eigensolver_factories/vqe_uccsd_factory.py

@@ -22,7 +22,7 @@
 from ....components.variational_forms import UCCSD
 from ....transformations import Transformation
 from ....transformations.fermionic_transformation import FermionicTransformation
-from ....components.initial_states import HartreeFock
+from ....circuit.library import HartreeFock
 
 from .minimum_eigensolver_factory import MinimumEigensolverFactory
 

qiskit/chemistry/applications/molecular_ground_state_energy.py

@@ -21,7 +21,7 @@
 from qiskit.aqua.algorithms import MinimumEigensolver, VQE
 from qiskit.aqua.operators import Z2Symmetries
 from qiskit.chemistry import QiskitChemistryError
-from qiskit.chemistry.components.initial_states import HartreeFock
+from qiskit.chemistry.circuit.library import HartreeFock
 from qiskit.chemistry.components.variational_forms import UCCSD
 from qiskit.chemistry.core import (Hamiltonian, TransformationType, QubitMappingType,
                                    ChemistryOperator, MolecularGroundStateResult)

qiskit/chemistry/circuit/library/__init__.py

@@ -0,0 +1,39 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2020.
+#
+# 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
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""
+===================================================================
+Chemistry Circuit Library (:mod:`qiskit.chemistry.circuit.library`)
+===================================================================
+
+A collection of circuits used as building blocks or inputs of algorithms in chemistry.
+
+.. currentmodule:: qiskit.chemistry.circuit.library
+
+Initial states
+==============
+
+.. autosummary::
+   :toctree: ../stubs/
+   :nosignatures:
+
+   HartreeFock
+   VSCF
+
+"""
+
+from .initial_states import (
+    HartreeFock,
+    VSCF
+)
+
+__all__ = ['HartreeFock', 'VSCF']

qiskit/chemistry/circuit/library/initial_states/__init__.py

@@ -0,0 +1,18 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2020.
+#
+# 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
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Initial state circuits."""
+
+from .hartree_fock import HartreeFock
+from .vscf import VSCF
+
+__all__ = ['HartreeFock', 'VSCF']