Add return-type to public functions, mostly tests part 2 (#7568)

Add return-type to public functions, mostly tests part 2

No change in the effective code.  A batch of ~50 files.

Modified files pass  ruff check --select=ANN201

Partially implements #4393

Author: pavoljuhas

cirq-core/cirq/contrib/noise_models/noise_models.py

@@ -45,7 +45,7 @@ def __init__(self, depol_prob: float, prepend: bool = False):
         self._prepend = prepend
 
     @property
-    def depol_prob(self):
+    def depol_prob(self) -> float:
         """The depolarizing probability."""
         return self._depol_prob
 
@@ -100,7 +100,7 @@ def __init__(self, bitflip_prob: float, prepend: bool = True):
         self._prepend = prepend
 
     @property
-    def bitflip_prob(self):
+    def bitflip_prob(self) -> float:
         """The probability of a bit-flip during measurement."""
         return self._bitflip_prob
 
@@ -154,7 +154,7 @@ def __init__(self, decay_prob: float, prepend: bool = True):
         self._prepend = prepend
 
     @property
-    def decay_prob(self):
+    def decay_prob(self) -> float:
         """The probability of T1 decay during measurement."""
         return self._decay_prob
 
@@ -207,12 +207,12 @@ def __init__(self, depol_prob: float, bitflip_prob: float):
         self.readout_noise_gate = ops.BitFlipChannel(bitflip_prob)
 
     @property
-    def depol_prob(self):
+    def depol_prob(self) -> float:
         """The depolarizing probability."""
         return self._depol_prob
 
     @property
-    def bitflip_prob(self):
+    def bitflip_prob(self) -> float:
         """The probability of a bit-flip during measurement."""
         return self._bitflip_prob
 
@@ -262,17 +262,17 @@ def __init__(self, depol_prob: float, bitflip_prob: float, decay_prob: float):
         self.readout_decay_gate = ops.AmplitudeDampingChannel(decay_prob)
 
     @property
-    def depol_prob(self):
+    def depol_prob(self) -> float:
         """The depolarizing probability."""
         return self._depol_prob
 
     @property
-    def bitflip_prob(self):
+    def bitflip_prob(self) -> float:
         """Probability of a bit-flip during measurement."""
         return self._bitflip_prob
 
     @property
-    def decay_prob(self):
+    def decay_prob(self) -> float:
         """The probability of T1 decay during measurement."""
         return self._decay_prob
 

cirq-core/cirq/contrib/quimb/grid_circuits.py

@@ -105,7 +105,7 @@ def _interaction(
     )
 
 
-def simplify_expectation_value_circuit(circuit_sand: cirq.Circuit):
+def simplify_expectation_value_circuit(circuit_sand: cirq.Circuit) -> None:
     """For low weight operators on low-degree circuits, we can simplify
     the circuit representation of an expectation value.
 

cirq-core/cirq/contrib/quimb/grid_circuits_test.py

@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+from typing import Sequence
+
 import networkx as nx
 import numpy as np
 import pytest
@@ -26,12 +28,13 @@ def _get_circuit(width, height, rs, p=2):
     return circuit, qubits
 
 
-def test_simplify_sandwich():
+def test_simplify_sandwich() -> None:
     rs = np.random.RandomState(52)
     for width in [2, 3]:
         for height in [1, 3]:
             for p in [1, 2]:
                 circuit, qubits = _get_circuit(width=width, height=height, p=p, rs=rs)
+                operator: cirq.PauliString
                 operator = cirq.PauliString(
                     {q: cirq.Z for q in rs.choice(qubits, size=2, replace=False)}
                 )
@@ -47,11 +50,12 @@ def test_simplify_sandwich():
 
 
 @pytest.mark.parametrize('simplify', [False, True])
-def test_circuit_to_tensors(simplify):
-    rs = np.random.RandomState(52)
+def test_circuit_to_tensors(simplify) -> None:
+    qubits: Sequence[cirq.Qid]
     qubits = cirq.LineQubit.range(2)
     circuit = cirq.testing.random_circuit(qubits=qubits, n_moments=10, op_density=0.8)
-    operator = cirq.PauliString({q: cirq.Z for q in rs.choice(qubits, size=2, replace=False)})
+    operator: cirq.PauliString
+    operator = cirq.PauliString(dict.fromkeys(qubits, cirq.Z))
 
     circuit_sand = ccq.circuit_for_expectation_value(circuit, operator)
     if simplify:
@@ -62,13 +66,14 @@ def test_circuit_to_tensors(simplify):
     np.testing.assert_allclose(u_tn, u_cirq, atol=1e-6)
 
 
-def test_tensor_expectation_value():
+def test_tensor_expectation_value() -> None:
     for _ in range(10):
         for width in [2, 3]:
             for height in [1, 3]:
                 for p in [1, 2]:
                     rs = np.random.RandomState(52)
                     circuit, qubits = _get_circuit(width=width, height=height, p=p, rs=rs)
+                    operator: cirq.PauliString
                     operator = cirq.PauliString(
                         {q: cirq.Z for q in rs.choice(qubits, size=2, replace=False)},
                         coefficient=rs.uniform(-1, 1),

cirq-core/cirq/contrib/quimb/mps_simulator.py

@@ -183,7 +183,7 @@ def __init__(self, sim_state: cirq.SimulationStateBase[MPSState]):
         super().__init__(sim_state)
 
     @property
-    def state(self):
+    def state(self) -> MPSState:
         return self._merged_sim_state
 
     def __str__(self) -> str:
@@ -646,10 +646,10 @@ def _act_on_fallback_(
         """Delegates the action to self.apply_op"""
         return self._state.apply_op(action, self.get_axes(qubits), self.prng)
 
-    def estimation_stats(self):
+    def estimation_stats(self) -> dict[str, float]:
         """Returns some statistics about the memory usage and quality of the approximation."""
         return self._state.estimation_stats()
 
     @property
-    def M(self):
+    def M(self) -> list[qtn.Tensor]:
         return self._state._M