Create tools to build operators

pulser-core/pulser/channels/base_channel.py

@@ -41,6 +41,20 @@
 
 STATES_RANK = get_args(States)
 
+
+def check_eigenbasis(states: list[States]) -> None:
+    """Checks that a list of states is an eigenbasis."""
+    indices = [STATES_RANK.index(state) for state in states]
+    if np.any(np.array(indices) == -1):
+        raise ValueError(f"States must be in {STATES_RANK}.")
+    if len(set(indices)) != len(indices):
+        raise ValueError("States can only appear once in eigenbasis.")
+    if np.sort(indices) != indices:
+        raise ValueError(
+            "Eigenstates must be ranked with highest energy first."
+        )
+
+
 EIGENSTATES: dict[str, list[States]] = {
     "ground-rydberg": ["r", "g"],
     "digital": ["g", "h"],

pulser-core/pulser/operators/hamiltonian.py

@@ -0,0 +1,38 @@
+# Copyright 2024 Pulser Development Team
+#
+# 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.
+"""A class to define the Pulser Hamiltonian."""
+from __future__ import annotations
+
+from pulser.operators.operator import TimeOperator
+from pulser import Sequence
+from pulser.register.base_register import BaseRegister
+from pulser.devices._device_datacls import BaseDevice
+from pulser.sampler.samples import SequenceSamples
+
+
+class Hamiltonian(TimeOperator):
+
+    @classmethod
+    def from_samples(
+        cls,
+        sampled_seq: SequenceSamples,
+        register: BaseRegister,
+        device: BaseDevice,
+        sampling_rate: float = 1.0,
+    ) -> Hamiltonian:
+        pass
+
+    @classmethod
+    def from_sequence(cls, sequence: Sequence) -> Hamiltonian:
+        pass