diff --git a/pyproject.toml b/pyproject.toml
index 82791b37..bbf3e129 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "oqd-core"
-version = "0.1.0"
+version = "0.2.0dev1"
 requires-python = ">=3.10"
 readme = "README.md"
 license = { text = "Apache 2.0" }
@@ -64,10 +64,7 @@ fixable = ["ALL"]
 oqd-compiler-infrastructure = { git = "https://github.com/openquantumdesign/oqd-compiler-infrastructure" }
 
 [dependency-groups]
-dev = [
-    "jupyter>=1.1.1",
-    "pre-commit>=4.1.0",
-]
+dev = ["jupyter>=1.1.1", "pre-commit>=4.1.0", "ruff>=0.13.1"]
 
 
 [project.urls]
diff --git a/src/oqd_core/backend.py b/src/oqd_core/backend.py
new file mode 100644
index 00000000..65d6dcf0
--- /dev/null
+++ b/src/oqd_core/backend.py
@@ -0,0 +1,79 @@
+# Copyright 2024-2025 Open Quantum Design
+
+# 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.
+
+
+import inspect
+import warnings
+from abc import ABC, abstractmethod
+from typing import Any
+
+########################################################################################
+
+__all__ = [
+    "MetaBackendRegistry",
+    "BackendRegistry",
+    "BackendBase",
+]
+
+########################################################################################
+
+
+class MetaBackendRegistry(type):
+    def __new__(cls, clsname, superclasses, attributedict):
+        attributedict["backends"] = dict()
+        return super().__new__(cls, clsname, superclasses, attributedict)
+
+    def register(cls, backend):
+        if not issubclass(backend, BackendBase):
+            raise TypeError("You may only register subclasses of BackendBase.")
+
+        if backend.__name__ in cls.backends.keys():
+            warnings.warn(
+                f"Overwriting previously registered backend `{backend.__name__}` of the same name.",
+                UserWarning,
+                stacklevel=2,
+            )
+
+        cls.backends[backend.__name__] = backend
+
+
+class BackendRegistry(metaclass=MetaBackendRegistry):
+    pass
+
+
+class BackendBase(ABC):
+    @abstractmethod
+    def run(self, program, args):
+        pass
+
+    def __init_subclass__(cls, **kwargs):
+        super().__init_subclass__(**kwargs)
+
+        args = inspect.getfullargspec(cls.run)
+
+        if "program" not in args.annotations:
+            warnings.warn(
+                f"Misisng type hint for argument `program` in run method of {cls.__name__}. Defaults to Any."
+            )
+
+            cls.run.__annotations__["program"] = Any
+
+        if "args" not in args.annotations:
+            warnings.warn(
+                f"Misisng type hint for argument `args` in run method of {cls.__name__}. Defaults to Any."
+            )
+
+            cls.run.__annotations__["args"] = Any
+
+        BackendRegistry.register(cls)
diff --git a/src/oqd_core/backend/__init__.py b/src/oqd_core/backend/__init__.py
deleted file mode 100644
index 084ae799..00000000
--- a/src/oqd_core/backend/__init__.py
+++ /dev/null
@@ -1,13 +0,0 @@
-# Copyright 2024-2025 Open Quantum Design
-
-# 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.
diff --git a/src/oqd_core/backend/base.py b/src/oqd_core/backend/base.py
deleted file mode 100644
index 1637d6d6..00000000
--- a/src/oqd_core/backend/base.py
+++ /dev/null
@@ -1,26 +0,0 @@
-# Copyright 2024-2025 Open Quantum Design
-
-# 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.
-
-
-from abc import ABC, abstractmethod
-
-########################################################################################
-
-
-class BackendBase(ABC):
-    @abstractmethod
-    def run(self, task):
-        pass
-
-    pass
diff --git a/src/oqd_core/backend/metric.py b/src/oqd_core/backend/metric.py
deleted file mode 100644
index eedcc3ef..00000000
--- a/src/oqd_core/backend/metric.py
+++ /dev/null
@@ -1,49 +0,0 @@
-# Copyright 2024-2025 Open Quantum Design
-
-# 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.
-
-from typing import List, Union
-
-from oqd_compiler_infrastructure import VisitableBaseModel
-from pydantic.types import NonNegativeInt
-
-########################################################################################
-from oqd_core.interface.analog.operator import OperatorSubtypes
-
-########################################################################################
-
-__all__ = [
-    "Expectation",
-    "EntanglementEntropyRenyi",
-    "EntanglementEntropyVN",
-]
-
-########################################################################################
-
-
-class Expectation(VisitableBaseModel):
-    operator: OperatorSubtypes
-
-
-class EntanglementEntropyVN(VisitableBaseModel):
-    qreg: List[NonNegativeInt] = []
-    qmode: List[NonNegativeInt] = []
-
-
-class EntanglementEntropyRenyi(VisitableBaseModel):
-    alpha: NonNegativeInt = 1
-    qreg: List[NonNegativeInt] = []
-    qmode: List[NonNegativeInt] = []
-
-
-Metric = Union[EntanglementEntropyVN, EntanglementEntropyRenyi, Expectation]
diff --git a/src/oqd_core/backend/task.py b/src/oqd_core/backend/task.py
deleted file mode 100644
index ac3d59ea..00000000
--- a/src/oqd_core/backend/task.py
+++ /dev/null
@@ -1,184 +0,0 @@
-# Copyright 2024-2025 Open Quantum Design
-
-# 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.
-
-from dataclasses import dataclass, field
-from typing import Annotated, Dict, List, Literal, Union
-
-import numpy as np
-from oqd_compiler_infrastructure import TypeReflectBaseModel
-from pydantic import BaseModel, BeforeValidator
-
-from oqd_core.backend.metric import Metric
-
-########################################################################################
-from oqd_core.interface.analog.operation import AnalogCircuit
-from oqd_core.interface.atomic.circuit import AtomicCircuit
-from oqd_core.interface.digital.circuit import DigitalCircuit
-
-########################################################################################
-
-
-class ComplexFloat(TypeReflectBaseModel):
-    """
-    Class representing a complex number
-
-    Attributes:
-        real (float): real part of the complex number.
-        imag (float): imaginary part of the complex number.
-    """
-
-    real: float
-    imag: float
-
-    @classmethod
-    def cast(cls, x):
-        if isinstance(x, ComplexFloat):
-            return x
-        if isinstance(x, complex):
-            return cls(real=x.real, imag=x.imag)
-        raise TypeError("Invalid type for argument x")
-
-    def __add__(self, other):
-        if isinstance(other, ComplexFloat):
-            self.real += other.real
-            self.imag += other.imag
-            return self
-
-        elif isinstance(other, (float, int)):
-            self.real += other
-            return self
-
-    def __mul__(self, other):
-        if isinstance(other, (float, int)):
-            self.real *= other
-            self.imag *= other
-            return self
-        elif isinstance(other, ComplexFloat):
-            real = self.real * other.real - self.imag * self.imag
-            imag = self.real * other.imag + self.imag * self.real
-            return ComplexFloat(real=real, imag=imag)
-        else:
-            raise TypeError
-
-    def __radd__(self, other):
-        return self + other
-
-    def __rmul__(self, other):
-        return self * other
-
-
-CastComplexFloat = Annotated[ComplexFloat, BeforeValidator(ComplexFloat.cast)]
-
-########################################################################################
-
-
-class TaskArgsBase(TypeReflectBaseModel):
-    layer: Literal["digital", "analog", "atomic"]
-
-
-class TaskResultsBase(TypeReflectBaseModel):
-    layer: Literal["digital", "analog", "atomic"]
-
-
-########################################################################################
-
-
-@dataclass
-class DataAnalog:
-    times: np.array = field(default_factory=lambda: np.empty(0))
-    state: np.array = field(default_factory=lambda: np.empty(0))
-    metrics: dict[str, List[Union[float, int]]] = field(default_factory=dict)
-    shots: np.array = field(default_factory=lambda: np.empty(0))
-
-
-class TaskArgsAnalog(TaskArgsBase):
-    layer: Literal["analog"] = "analog"
-    n_shots: Union[int, None] = 10
-    fock_cutoff: int = 4
-    dt: float = 0.1
-    metrics: Dict[str, Metric] = {}
-
-
-class TaskResultAnalog(TaskResultsBase):
-    """
-    Contains the results of a simulation/actual experiment.
-
-    Attributes:
-        layer (str): the layer of the experiment (analog, atomic)
-        times (List[float]): number of discrete times
-        state (List[ComplexFloat]): Final quantum state after evolution
-        metrics (Dict): metrics which have been computed for the experiment. This does not require any Measure instruction in the analog layer.
-        counts (Dict[str, int]): counts of different states after the experiment. This requires Measure instruction in the analog layer.
-        runtime (float): time taken for the simulation/experiment.
-    """
-
-    layer: Literal["analog"] = "analog"
-    times: List[float] = []
-    state: List[CastComplexFloat] = []
-    metrics: Dict[str, List[Union[float, int]]] = {}
-    counts: Dict[str, int] = {}
-    runtime: float = None
-
-
-# todo: uncomment when Digital layer is further developed.
-class TaskArgsDigital(BaseModel):
-    layer: Literal["digital"] = "digital"
-    repetitions: int = 10
-
-
-class TaskResultDigital(BaseModel):
-    layer: Literal["digital"] = "digital"
-    counts: dict[str, int] = {}
-    state: List[CastComplexFloat] = []
-
-
-#
-
-########################################################################################
-
-
-# todo: move to TriCal package
-class TaskArgsAtomic(BaseModel):
-    layer: Literal["atomic"] = "atomic"
-    n_shots: int = 10
-    fock_trunc: int = 4
-    dt: float = 0.1
-
-
-class TaskResultAtomic(BaseModel):
-    layer: Literal["atomic"] = "atomic"
-    # Hardware results
-    collated_state_readout: dict[int, int] = {}
-    state_readout: dict[int, int] = {}
-
-
-########################################################################################
-
-
-class Task(TypeReflectBaseModel):
-    """
-    Class representing a task to run a quantum experiment with some arguments
-
-    Attributes:
-        program (Union[AnalogCircuit, DigitalCircuit, AtomicCircuit]): Quantum experiment to run
-        args (Union[analog_sim.base.TaskArgsAnalogSimulator, TaskArgsDigital, TaskArgsAtomic]): Arguments for the quantum experiment
-    """
-
-    program: Union[AnalogCircuit, DigitalCircuit, AtomicCircuit]
-    args: Union[TaskArgsAnalog, TaskArgsDigital, TaskArgsAtomic]
-
-
-TaskResult = Union[TaskResultAnalog, TaskResultAtomic, TaskResultDigital]
-
-########################################################################################
diff --git a/src/oqd_core/compiler/analog/passes/__init__.py b/src/oqd_core/compiler/analog/passes/__init__.py
index 3b53023a..17ad3021 100644
--- a/src/oqd_core/compiler/analog/passes/__init__.py
+++ b/src/oqd_core/compiler/analog/passes/__init__.py
@@ -13,12 +13,11 @@
 # limitations under the License.
 
 from .analysis import analysis_canonical_hamiltonian_dim, analysis_term_index
-from .assign import assign_analog_circuit_dim, verify_analog_args_dim
+from .assign import assign_analog_circuit_dim
 from .canonicalize import analog_operator_canonicalization
 
 __all__ = [
     "assign_analog_circuit_dim",
-    "verify_analog_args_dim",
     "analog_operator_canonicalization",
     "analysis_canonical_hamiltonian_dim",
     "analysis_term_index",
diff --git a/src/oqd_core/compiler/analog/passes/assign.py b/src/oqd_core/compiler/analog/passes/assign.py
index 96eef144..8ae1e811 100644
--- a/src/oqd_core/compiler/analog/passes/assign.py
+++ b/src/oqd_core/compiler/analog/passes/assign.py
@@ -17,7 +17,6 @@
 ########################################################################################
 from oqd_core.compiler.analog.rewrite.assign import AssignAnalogIRDim
 from oqd_core.compiler.analog.verify.task import (
-    VerifyAnalogArgsDim,
     VerifyAnalogCircuitDim,
 )
 
@@ -25,7 +24,6 @@
 
 __all__ = [
     "assign_analog_circuit_dim",
-    "verify_analog_args_dim",
 ]
 
 ########################################################################################
@@ -51,20 +49,3 @@ def assign_analog_circuit_dim(model):
         )
     )(assigned_model)
     return assigned_model
-
-
-def verify_analog_args_dim(model, n_qreg, n_qmode):
-    """
-    This pass checks whether the assigned n_qreg and n_qmode in AnalogCircuit match the n_qreg and n_qmode
-    in any Operators (like the Operator inside Expectation) in TaskArgsAnalog
-
-    Args:
-        model (TaskArgsAnalog):
-
-    Returns:
-        model (TaskArgsAnalog):
-
-    Assumptions:
-        All  [`Operator`][oqd_core.interface.analog.operator.Operator] inside TaskArgsAnalog must be canonicalized
-    """
-    Post(VerifyAnalogArgsDim(n_qreg=n_qreg, n_qmode=n_qmode))(model)
diff --git a/src/oqd_core/compiler/analog/rewrite/canonicalize.py b/src/oqd_core/compiler/analog/rewrite/canonicalize.py
index b5f45347..5fef7b3b 100644
--- a/src/oqd_core/compiler/analog/rewrite/canonicalize.py
+++ b/src/oqd_core/compiler/analog/rewrite/canonicalize.py
@@ -386,9 +386,6 @@ def __init__(self):
     def map_AnalogGate(self, model):
         self.op_add_root = False
 
-    def map_Expectation(self, model):
-        self.op_add_root = False
-
     def map_Operator(self, model: Operator):
         if not self.op_add_root:
             self.op_add_root = True
diff --git a/src/oqd_core/compiler/analog/verify/__init__.py b/src/oqd_core/compiler/analog/verify/__init__.py
index 36d70158..34852b58 100644
--- a/src/oqd_core/compiler/analog/verify/__init__.py
+++ b/src/oqd_core/compiler/analog/verify/__init__.py
@@ -25,7 +25,6 @@
 )
 from .operator import VerifyHilberSpaceDim
 from .task import (
-    VerifyAnalogArgsDim,
     VerifyAnalogCircuitDim,
 )
 
@@ -40,6 +39,5 @@
     "CanVerSortedOrder",
     "CanVerScaleTerm",
     "VerifyAnalogCircuitDim",
-    "VerifyAnalogArgsDim",
     "VerifyHilberSpaceDim",
 ]
diff --git a/src/oqd_core/compiler/analog/verify/canonicalize.py b/src/oqd_core/compiler/analog/verify/canonicalize.py
index 5be663cf..0199230e 100644
--- a/src/oqd_core/compiler/analog/verify/canonicalize.py
+++ b/src/oqd_core/compiler/analog/verify/canonicalize.py
@@ -385,9 +385,6 @@ def __init__(self):
     def map_AnalogGate(self, model):
         self._single_term_scaling_needed = False
 
-    def map_Expectation(self, model):
-        self._single_term_scaling_needed = False
-
     def map_OperatorScalarMul(self, model: OperatorScalarMul):
         self._single_term_scaling_needed = True
         pass
diff --git a/src/oqd_core/compiler/analog/verify/operator.py b/src/oqd_core/compiler/analog/verify/operator.py
index 94affb00..6efb8732 100644
--- a/src/oqd_core/compiler/analog/verify/operator.py
+++ b/src/oqd_core/compiler/analog/verify/operator.py
@@ -71,9 +71,6 @@ def _reset(self):
     def map_AnalogGate(self, model):
         self._reset()
 
-    def map_Expectation(self, model):
-        self._reset()
-
     def _get_dim(self, model):
         if isinstance(model, Pauli):
             return (1, 0)
@@ -103,14 +100,14 @@ def map_OperatorAdd(self, model):
             assert self._term_dim == new, "Incorrect Hilbert space dimension"
 
         if isinstance(model.op1, Union[OperatorTerminal, OperatorMul]):
-            assert self._term_dim == self._get_dim(model.op1), (
-                "Incorrect Hilbert space dimension"
-            )
+            assert self._term_dim == self._get_dim(
+                model.op1
+            ), "Incorrect Hilbert space dimension"
         elif isinstance(model.op1, OperatorScalarMul):
             if isinstance(model.op1.op, Union[OperatorTerminal, OperatorMul]):
-                assert self._term_dim == self._get_dim(model.op1.op), (
-                    "Incorrect Hilbert space dimension"
-                )
+                assert self._term_dim == self._get_dim(
+                    model.op1.op
+                ), "Incorrect Hilbert space dimension"
 
         if not isinstance(model.op1, OperatorAdd):
             self._final_add_term = True
diff --git a/src/oqd_core/compiler/analog/verify/task.py b/src/oqd_core/compiler/analog/verify/task.py
index b2f7e9f9..6534af7e 100644
--- a/src/oqd_core/compiler/analog/verify/task.py
+++ b/src/oqd_core/compiler/analog/verify/task.py
@@ -14,7 +14,6 @@
 
 from oqd_compiler_infrastructure import RewriteRule
 
-from oqd_core.backend.metric import Expectation
 from oqd_core.compiler.analog.passes.analysis import analysis_canonical_hamiltonian_dim
 
 ########################################################################################
@@ -24,7 +23,6 @@
 
 __all__ = [
     "VerifyAnalogCircuitDim",
-    "VerifyAnalogArgsDim",
 ]
 
 ########################################################################################
@@ -51,32 +49,6 @@ def __init__(self, n_qreg, n_qmode):
         self._dim: tuple = (n_qreg, n_qmode)
 
     def map_AnalogGate(self, model: AnalogGate):
-        assert self._dim == analysis_canonical_hamiltonian_dim(model.hamiltonian), (
-            "Inconsistent Hilbert space dimension between Analog Gates"
-        )
-
-
-class VerifyAnalogArgsDim(RewriteRule):
-    """
-    Checks whether hilbert space dimensions are consistent between Expectation in args
-    and whether they match the n_qreg and n_qmode given as input.
-
-    Args:
-        model (VisitableBaseModel):
-            The rule only verfies Expectation inside TaskArgsAnalog in Analog layer
-
-    Returns:
-        model (VisitableBaseModel): unchanged
-
-    Assumptions:
-        All [`Operator`][oqd_core.interface.analog.operator.Operator] inside  [`AnalogCircuit`][oqd_core.interface.analog.operations.AnalogCircuit] are canonicalized
-    """
-
-    def __init__(self, n_qreg, n_qmode):
-        super().__init__()
-        self._dim: tuple = (n_qreg, n_qmode)
-
-    def map_Expectation(self, model: Expectation):
-        assert self._dim == analysis_canonical_hamiltonian_dim(model.operator), (
-            "Inconsistent Hilbert space dimension in Expectation metric"
-        )
+        assert self._dim == analysis_canonical_hamiltonian_dim(
+            model.hamiltonian
+        ), "Inconsistent Hilbert space dimension between Analog Gates"
diff --git a/src/oqd_core/interface/analog/__init__.py b/src/oqd_core/interface/analog/__init__.py
index f3be5146..5901a49a 100644
--- a/src/oqd_core/interface/analog/__init__.py
+++ b/src/oqd_core/interface/analog/__init__.py
@@ -31,7 +31,7 @@
     OperatorMul,
     OperatorScalarMul,
     OperatorSub,
-    OperatorSubtypes,
+    OperatorSubTypes,
     OperatorTerminal,
     Pauli,
     PauliI,
@@ -43,7 +43,7 @@
 )
 
 __all__ = [
-    "OperatorSubtypes",
+    "OperatorSubTypes",
     "Operator",
     "OperatorTerminal",
     "Pauli",
diff --git a/src/oqd_core/interface/analog/operation.py b/src/oqd_core/interface/analog/operation.py
index 8b8e7f00..90394d8b 100644
--- a/src/oqd_core/interface/analog/operation.py
+++ b/src/oqd_core/interface/analog/operation.py
@@ -12,13 +12,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import List, Literal, Union
+from __future__ import annotations
 
-# %%
-from oqd_compiler_infrastructure import TypeReflectBaseModel, VisitableBaseModel
+from typing import Annotated, List, Optional, Union
+
+from oqd_compiler_infrastructure import TypeReflectBaseModel
+from pydantic import Discriminator
 from pydantic.types import NonNegativeInt
 
-from oqd_core.interface.analog.operator import OperatorSubtypes
+from oqd_core.interface.analog.operator import OperatorSubTypes
 
 __all__ = [
     "AnalogCircuit",
@@ -33,24 +35,26 @@
 ########################################################################################
 
 
-class AnalogGate(TypeReflectBaseModel):
+class AnalogOperation(TypeReflectBaseModel):
     """
-    Class representing an analog gate composed of Hamiltonian terms and dissipation terms
-
-    Attributes:
-        hamiltonian (Operator): Hamiltonian terms of the gate
+    Class representing an analog operation applied to the quantum system
     """
 
-    hamiltonian: OperatorSubtypes
+    pass
+
+
+########################################################################################
 
 
-# %%
-class AnalogOperation(VisitableBaseModel):
+class AnalogGate(TypeReflectBaseModel):
     """
-    Class representing an analog operation applied to the quantum system
+    Class representing an analog gate composed of Hamiltonian terms and dissipation terms
+
+    Attributes:
+        hamiltonian (Operator): Hamiltonian terms of the gate
     """
 
-    pass
+    hamiltonian: OperatorSubTypes
 
 
 class Evolve(AnalogOperation):
@@ -62,9 +66,11 @@ class Evolve(AnalogOperation):
         gate (AnalogGate): Analog gate to evolve by
     """
 
-    key: Literal["evolve"] = "evolve"
     duration: float
-    gate: Union[AnalogGate, str]
+    gate: AnalogGate
+
+
+########################################################################################
 
 
 class Measure(AnalogOperation):
@@ -72,7 +78,7 @@ class Measure(AnalogOperation):
     Class representing a measurement in the analog circuit
     """
 
-    key: Literal["measure"] = "measure"
+    targets: Optional[List[int]] = None
 
 
 class Initialize(AnalogOperation):
@@ -80,13 +86,20 @@ class Initialize(AnalogOperation):
     Class representing a initialization in the analog circuit
     """
 
-    key: Literal["initialize"] = "initialize"
+    targets: Optional[List[int]] = None
 
 
+########################################################################################
+
 """
-Union of classes 
+Union of classes
 """
-Statement = Union[Measure, Evolve, Initialize]
+AnalogOperationSubTypes = Annotated[
+    Union[Measure, Evolve, Initialize], Discriminator(discriminator="class_")
+]
+
+
+########################################################################################
 
 
 class AnalogCircuit(AnalogOperation):
@@ -98,7 +111,7 @@ class AnalogCircuit(AnalogOperation):
 
     """
 
-    sequence: List[Statement] = []
+    sequence: List[AnalogOperationSubTypes] = []
 
     n_qreg: Union[NonNegativeInt, None] = None
     n_qmode: Union[NonNegativeInt, None] = None
@@ -106,8 +119,8 @@ class AnalogCircuit(AnalogOperation):
     def evolve(self, gate: AnalogGate, duration: float):
         self.sequence.append(Evolve(duration=duration, gate=gate))
 
-    def initialize(self):
-        self.sequence.append(Initialize())
+    def initialize(self, targets=None):
+        self.sequence.append(Initialize(targets=targets))
 
-    def measure(self):
-        self.sequence.append(Measure())
+    def measure(self, targets=None):
+        self.sequence.append(Measure(targets=targets))
diff --git a/src/oqd_core/interface/analog/operator.py b/src/oqd_core/interface/analog/operator.py
index fc79af37..0583b3cb 100644
--- a/src/oqd_core/interface/analog/operator.py
+++ b/src/oqd_core/interface/analog/operator.py
@@ -14,14 +14,15 @@
 
 from __future__ import annotations
 
-from typing import Union
+from typing import Annotated, Union
 
 from oqd_compiler_infrastructure import TypeReflectBaseModel
+from pydantic import Discriminator
 
 ########################################################################################
 from oqd_core.interface.math import (
     MathExpr,
-    MathExprSubtypes,
+    MathExprSubTypes,
     MathImag,
     MathMul,
     MathNum,
@@ -49,7 +50,7 @@
     "OperatorMul",
     "OperatorScalarMul",
     "OperatorKron",
-    "OperatorSubtypes",
+    "OperatorSubTypes",
 ]
 
 
@@ -223,8 +224,8 @@ class OperatorScalarMul(Operator):
         expr (MathExpr): [`MathExpr`][oqd_core.interface.math.MathExpr] to multiply by
     """
 
-    op: OperatorSubtypes
-    expr: MathExprSubtypes
+    op: OperatorSubTypes
+    expr: MathExprSubTypes
 
 
 class OperatorBinaryOp(Operator):
@@ -244,8 +245,8 @@ class OperatorAdd(OperatorBinaryOp):
         op2 (Operator): Right hand side [`Operator`][oqd_core.interface.analog.operator.Operator]
     """
 
-    op1: OperatorSubtypes
-    op2: OperatorSubtypes
+    op1: OperatorSubTypes
+    op2: OperatorSubTypes
 
 
 class OperatorSub(OperatorBinaryOp):
@@ -257,8 +258,8 @@ class OperatorSub(OperatorBinaryOp):
         op2 (Operator): Right hand side [`Operator`][oqd_core.interface.analog.operator.Operator]
     """
 
-    op1: OperatorSubtypes
-    op2: OperatorSubtypes
+    op1: OperatorSubTypes
+    op2: OperatorSubTypes
 
 
 class OperatorMul(OperatorBinaryOp):
@@ -270,8 +271,8 @@ class OperatorMul(OperatorBinaryOp):
         op2 (Operator): Right hand side [`Operator`][oqd_core.interface.analog.operator.Operator]
     """
 
-    op1: OperatorSubtypes
-    op2: OperatorSubtypes
+    op1: OperatorSubTypes
+    op2: OperatorSubTypes
 
 
 class OperatorKron(OperatorBinaryOp):
@@ -283,25 +284,28 @@ class OperatorKron(OperatorBinaryOp):
         op2 (Operator): Right hand side [`Operator`][oqd_core.interface.analog.operator.Operator]
     """
 
-    op1: OperatorSubtypes
-    op2: OperatorSubtypes
+    op1: OperatorSubTypes
+    op2: OperatorSubTypes
 
 
 ########################################################################################
 
-OperatorSubtypes = Union[
-    PauliI,
-    PauliX,
-    PauliY,
-    PauliZ,
-    Creation,
-    Annihilation,
-    Identity,
-    OperatorAdd,
-    OperatorSub,
-    OperatorMul,
-    OperatorScalarMul,
-    OperatorKron,
+OperatorSubTypes = Annotated[
+    Union[
+        PauliI,
+        PauliX,
+        PauliY,
+        PauliZ,
+        Creation,
+        Annihilation,
+        Identity,
+        OperatorAdd,
+        OperatorSub,
+        OperatorMul,
+        OperatorScalarMul,
+        OperatorKron,
+    ],
+    Discriminator(discriminator="class_"),
 ]
 """
 Alias for the union of concrete Operator subtypes
diff --git a/src/oqd_core/interface/atomic/protocol.py b/src/oqd_core/interface/atomic/protocol.py
index e05afde1..efced645 100644
--- a/src/oqd_core/interface/atomic/protocol.py
+++ b/src/oqd_core/interface/atomic/protocol.py
@@ -14,10 +14,10 @@
 
 from __future__ import annotations
 
-from typing import List, Tuple, Union
+from typing import Annotated, List, Tuple, Union
 
 from oqd_compiler_infrastructure import TypeReflectBaseModel
-from pydantic import conlist
+from pydantic import Discriminator, conlist
 
 from oqd_core.interface.atomic.system import Transition
 from oqd_core.interface.math import CastMathExpr, ConstantMathExpr
@@ -103,7 +103,7 @@ class ParallelProtocol(Protocol):
         sequence: List of pulses or subprotocols to compose together in a parallel fashion.
     """
 
-    sequence: List[Union[PulseSubTypes, ProtocolSubTypes]]
+    sequence: List[ProtocolPulseSubTypes]
 
 
 class SequentialProtocol(Protocol):
@@ -114,8 +114,16 @@ class SequentialProtocol(Protocol):
         sequence: List of pulses or subprotocols to compose together in a sequntial fashion.
     """
 
-    sequence: List[Union[PulseSubTypes, ProtocolSubTypes]]
+    sequence: List[ProtocolPulseSubTypes]
 
 
-ProtocolSubTypes = Union[SequentialProtocol, ParallelProtocol]
-PulseSubTypes = Union[Pulse, MeasurePulse]
+ProtocolSubTypes = Annotated[
+    Union[SequentialProtocol, ParallelProtocol], Discriminator(discriminator="class_")
+]
+PulseSubTypes = Annotated[
+    Union[Pulse, MeasurePulse], Discriminator(discriminator="class_")
+]
+ProtocolPulseSubTypes = Annotated[
+    Union[SequentialProtocol, ParallelProtocol, Pulse, MeasurePulse],
+    Discriminator(discriminator="class_"),
+]
diff --git a/src/oqd_core/interface/math.py b/src/oqd_core/interface/math.py
index 7d936399..724f8569 100644
--- a/src/oqd_core/interface/math.py
+++ b/src/oqd_core/interface/math.py
@@ -48,7 +48,7 @@
     "MathMul",
     "MathDiv",
     "MathPow",
-    "MathExprSubtypes",
+    "MathExprSubTypes",
     "ConstantMathExpr",
     "CastMathExpr",
 ]
@@ -339,27 +339,25 @@ class MathPow(MathBinaryOp):
 
 ########################################################################################
 
-MathExprSubtypes = Annotated[
+MathExprSubTypes = Annotated[
     Union[
-        Annotated[MathNum, Tag("MathNum")],
-        Annotated[MathVar, Tag("MathVar")],
-        Annotated[MathImag, Tag("MathImag")],
-        Annotated[MathFunc, Tag("MathFunc")],
-        Annotated[MathAdd, Tag("MathAdd")],
-        Annotated[MathSub, Tag("MathSub")],
-        Annotated[MathMul, Tag("MathMul")],
-        Annotated[MathDiv, Tag("MathDiv")],
-        Annotated[MathPow, Tag("MathPow")],
+        MathNum,
+        MathVar,
+        MathImag,
+        MathFunc,
+        MathAdd,
+        MathSub,
+        MathMul,
+        MathDiv,
+        MathPow,
     ],
-    Discriminator(
-        lambda v: v["class_"] if isinstance(v, dict) else getattr(v, "class_")
-    ),
+    Discriminator(discriminator="class_"),
 ]
 """
 Alias for the union of concrete MathExpr subtypes
 """
 
-CastMathExpr = Annotated[MathExprSubtypes, BeforeValidator(MathExpr.cast)]
+CastMathExpr = Annotated[MathExprSubTypes, BeforeValidator(MathExpr.cast)]
 """
 Annotated type that cast typical numeric python types to MathExpr
 """
diff --git a/uv.lock b/uv.lock
index 790b68f2..447e6f97 100644
--- a/uv.lock
+++ b/uv.lock
@@ -1461,14 +1461,14 @@ wheels = [
 [[package]]
 name = "oqd-compiler-infrastructure"
 version = "0.1.0"
-source = { git = "https://github.com/openquantumdesign/oqd-compiler-infrastructure#b744a07a769e3a4107a128acb662586156608526" }
+source = { git = "https://github.com/openquantumdesign/oqd-compiler-infrastructure#bba1bb47c3fdde9c10be1ab373abf3a223b4c339" }
 dependencies = [
     { name = "pydantic" },
 ]
 
 [[package]]
 name = "oqd-core"
-version = "0.1.0"
+version = "0.2.0.dev1"
 source = { editable = "." }
 dependencies = [
     { name = "numpy", version = "2.2.6", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version < '3.11'" },
@@ -1495,6 +1495,7 @@ tests = [
 dev = [
     { name = "jupyter" },
     { name = "pre-commit" },
+    { name = "ruff" },
 ]
 
 [package.metadata]
@@ -1515,6 +1516,7 @@ requires-dist = [
 dev = [
     { name = "jupyter", specifier = ">=1.1.1" },
     { name = "pre-commit", specifier = ">=4.1.0" },
+    { name = "ruff", specifier = ">=0.13.1" },
 ]
 
 [[package]]
@@ -2204,6 +2206,32 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/ce/08/4349bdd5c64d9d193c360aa9db89adeee6f6682ab8825dca0a3f535f434f/rpds_py-0.27.1-pp311-pypy311_pp73-musllinux_1_2_x86_64.whl", hash = "sha256:dc23e6820e3b40847e2f4a7726462ba0cf53089512abe9ee16318c366494c17a", size = 556523 },
 ]
 
+[[package]]
+name = "ruff"
+version = "0.13.1"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/ab/33/c8e89216845615d14d2d42ba2bee404e7206a8db782f33400754f3799f05/ruff-0.13.1.tar.gz", hash = "sha256:88074c3849087f153d4bb22e92243ad4c1b366d7055f98726bc19aa08dc12d51", size = 5397987 }
+wheels = [
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+    { url = "https://files.pythonhosted.org/packages/ff/84/ba378ef4129415066c3e1c80d84e539a0d52feb250685091f874804f28af/ruff-0.13.1-py3-none-macosx_10_12_x86_64.whl", hash = "sha256:4ee9f4249bf7f8bb3984c41bfaf6a658162cdb1b22e3103eabc7dd1dc5579334", size = 12937258 },
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+]
+
 [[package]]
 name = "scipy"
 version = "1.15.3"