[WIP] VQE submodule

dwave/gate/operations/operations.py

@@ -29,6 +29,7 @@
     "Y",
     "Z",
     "Hadamard",
+    "HY",
     "Phase",
     "S",  # alias
     "P",  # alias
@@ -231,6 +232,26 @@ def matrix(cls) -> NDArray[np.complex128]:
         matrix = math.sqrt(2) / 2 * np.array([[1.0, 1.0], [1.0, -1.0]], dtype=np.complex128)
         return matrix
 
+class HY(Operation):
+    """Self-inverse operation for Y-Z basis swap.
+
+    Has the property $\sigma_y = H_y \sigma_z H_y.
+
+    Args:
+        qubits: Qubits on which the operation should be applied. Only
+            required when applying an operation within a circuit context.
+    """
+
+    _num_qubits: int = 1
+
+    # see: https://quantumcomputing.stackexchange.com/questions/11390/problem-with-commutation-of-e-ih-1t-and-e-ih-2t-where-h-1-commutes/11391#11391
+    # not the only way of doing this, but the most simple
+
+    @mixedproperty
+    def matrix(cls) -> NDArray[np.complex128]:
+        """The matrix representation of the $H_y$ operator."""
+        return math.sqrt(2) / 2 * np.array([[1, -1j], [1j, -1]], dtype=np.complex128)
+
 
 class S(Operation):
     """S (Phase) operation.

dwave/gate/vqe/__init__.py

@@ -0,0 +1,21 @@
+# Copyright 2023 D-Wave Systems Inc.
+#
+#    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
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    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.
+
+"""Module for running the Variational Quantum Eigensolver (VQE) algorithm.
+
+TODO: Add description
+"""
+from dwave.gate.vqe.operators import *
+from dwave.gate.vqe.transformations.jordan_wigner import *
+from dwave.gate.vqe.vqe import *

dwave/gate/vqe/cqm_partition.py

@@ -0,0 +1,68 @@
+# Copyright 2023 D-Wave Systems Inc.
+#
+#    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
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    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.
+
+__all__ = [
+    "partition_cqm",
+]
+
+import warnings
+
+
+try:
+    import dimod
+
+    from dwave.system import LeapHybridCQMSampler
+except ImportError as e:
+    raise ImportError("Dimod must be installed for CQM partioning.") from e
+
+
+def partition_cqm(adjacency, num_measurements):
+    """TODO"""
+    cqm = dimod.ConstrainedQuadraticModel()
+
+    measurement_rounds = [
+        dimod.Integer(i, lower_bound=0, upper_bound=num_measurements)
+        for i in range(num_measurements)
+    ]
+
+    cqm.set_objective(sum(measurement_rounds))
+
+    for source, target in adjacency:
+        cqm.add_constraint_from_comparison(
+            measurement_rounds[source] ** 2
+            + measurement_rounds[target] ** 2
+            - 2 * measurement_rounds[source] * measurement_rounds[target]
+            >= 1
+        )
+
+    sampler = LeapHybridCQMSampler()
+
+    sampleset = sampler.sample_cqm(cqm)
+    sampleset = sampleset.filter(lambda x: x.is_feasible)
+
+    if len(sampleset) == 0:
+        warnings.warn("No feasible measurement schemes found, defaulting to sequential measurement")
+        cqm_sample = {i: i for i in range(num_measurements)}
+    else:
+        cqm_sample = sampleset.first.sample
+
+    partition = {}
+
+    for pauli_index, measurement_round in cqm_sample.items():
+        if measurement_round not in partition:
+            partition[measurement_round] = [pauli_index]
+        else:
+            partition[measurement_round] = partition[measurement_round] + [pauli_index]
+
+    return partition