fix type checking list -> List

mitiq/qse/qse.py

@@ -43,7 +43,7 @@ def execute_with_qse(
     Returns:
         The expectation value estimated with QSE.
     """
-    P = get_projector(
+    projector = get_projector(
         circuit,
         executor,
         check_operators,
@@ -54,12 +54,15 @@ def execute_with_qse(
     pop = get_expectation_value_for_observable(
         circuit,
         executor,
-        P * observable * P,
+        projector * observable * projector,
         pauli_string_to_expectation_cache,
     )
     # Compute the normalization factor: <P P>
     pp = get_expectation_value_for_observable(
-        circuit, executor, P * P, pauli_string_to_expectation_cache
+        circuit,
+        executor,
+        projector * projector,
+        pauli_string_to_expectation_cache,
     )
     return pop / pp
 

mitiq/qse/qse_utils.py

@@ -5,7 +5,7 @@
 
 """Functions for computing the projector for subspace expansion."""
 
-from typing import Callable, Sequence, Union, Dict
+from typing import Callable, Sequence, Union, Dict, List
 from mitiq import Observable, QPROGRAM, QuantumResult, PauliString
 import numpy as np
 import numpy.typing as npt
@@ -91,7 +91,7 @@ def _compute_overlap_matrix(
     check_operators: Sequence[PauliString],
     pauli_string_to_expectation_cache: Dict[PauliString, complex] = {},
 ) -> npt.NDArray[np.float64]:
-    S: list[list[float]] = []
+    S: List[List[float]] = []
     # S_ij = <Ψ|Mi† Mj|Ψ>
     for i in range(len(check_operators)):
         S.append([])
@@ -113,7 +113,7 @@ def _compute_hamiltonian_overlap_matrix(
     code_hamiltonian: Observable,
     pauli_string_to_expectation_cache: Dict[PauliString, complex] = {},
 ) -> npt.NDArray[np.float64]:
-    H: list[list[float]] = []
+    H: List[List[float]] = []
     # H_ij = <Ψ|Mi† H Mj|Ψ>
     for i in range(len(check_operators)):
         H.append([])

mitiq/qse/tests/test_qse.py

@@ -67,24 +67,30 @@ def test_execute_with_qse():
         code_hamiltonian,
     ) = get_5_1_3_code_check_operators_and_code_hamiltonian()
     observable = get_observable_in_code_space(PauliString("ZZZZZ"))
+    unmitigated_value = observable.expectation(
+        qc, execute_with_depolarized_noise
+    )
     mitigated_value = execute_with_qse(
         qc,
         execute_with_depolarized_noise,
         check_operators,
         code_hamiltonian,
         observable,
     )
-    assert abs(mitigated_value.real - 1) < 0.001
+    assert abs(mitigated_value.real - 1) < abs(unmitigated_value.real - 1)
 
     observable = get_observable_in_code_space(PauliString("XXXXX"))
+    unmitigated_value = observable.expectation(
+        qc, execute_with_depolarized_noise
+    )
     mitigated_value = execute_with_qse(
         qc,
         execute_with_depolarized_noise,
         check_operators,
         code_hamiltonian,
         observable,
     )
-    assert abs(mitigated_value.real - 0.5) < 0.001
+    assert abs(mitigated_value.real - 0.5) < abs(unmitigated_value.real - 0.5)
 
 
 def test_mitigate_executor():
@@ -107,13 +113,16 @@ def test_mitigate_executor():
         code_hamiltonian,
         observable,
     )
+    unmitigated_value = observable.expectation(
+        qc, execute_with_depolarized_noise
+    )
     mitigated_value = mitigated_executor(qc)
-    assert abs(mitigated_value.real - 1) < 0.001
+    assert abs(mitigated_value.real - 1) < abs(unmitigated_value.real - 1)
 
     batched_mitigated_values = batched_mitigated_executor([qc] * 3)
     assert all(
         [
-            abs(mitigated_value.real - 1) < 0.001
+            abs(mitigated_value.real - 1) < abs(unmitigated_value.real - 1)
             for mitigated_value in batched_mitigated_values
         ]
     )
@@ -131,13 +140,16 @@ def test_mitigate_executor():
         code_hamiltonian,
         observable,
     )
+    unmitigated_value = observable.expectation(
+        qc, execute_with_depolarized_noise
+    )
     mitigated_value = mitigated_executor(qc)
-    assert abs(mitigated_value.real - 0.5) < 0.001
+    assert abs(mitigated_value.real - 0.5) < abs(unmitigated_value.real - 0.5)
 
     batched_mitigated_values = batched_mitigated_executor([qc] * 3)
     assert all(
         [
-            abs(mitigated_value.real - 0.5) < 0.001
+            abs(mitigated_value.real - 0.5) < abs(unmitigated_value.real - 0.5)
             for mitigated_value in batched_mitigated_values
         ]
     )
@@ -163,8 +175,11 @@ def decorated_executor(circuit: QPROGRAM) -> np.ndarray:
             noise_level=(0.01,),
         )
 
+    unmitigated_value = observable.expectation(
+        qc, execute_with_depolarized_noise
+    )
     mitigated_value = decorated_executor(qc)
-    assert abs(mitigated_value.real - 1) < 0.001
+    assert abs(mitigated_value.real - 1) < abs(unmitigated_value.real - 1)
 
     observable = get_observable_in_code_space(PauliString("XXXXX"))
 
@@ -180,8 +195,11 @@ def decorated_executor(circuit: QPROGRAM) -> np.ndarray:
             noise_level=(0.01,),
         )
 
+    unmitigated_value = observable.expectation(
+        qc, execute_with_depolarized_noise
+    )
     mitigated_value = decorated_executor(qc)
-    assert abs(mitigated_value.real - 0.5) < 0.001
+    assert abs(mitigated_value.real - 0.5) < abs(unmitigated_value.real - 0.5)
 
 
 def test_get_projector():
@@ -249,7 +267,7 @@ def test_compute_hamiltonian_overlap_matrix():
     assert H[0][0].real > -16
 
 
-def get_observable_in_code_space(observable: list[cirq.PauliString]):
+def get_observable_in_code_space(observable: List[cirq.PauliString]):
     FIVE_I = PauliString("IIIII")
     projector_onto_code_space = [
         PauliString("XZZXI"),