赛前稳定版

tests/test_cpu_backend.py

@@ -5,7 +5,10 @@ from qibo import Circuit, gates, hamiltonians
 from qibo.symbols import X, Z
 
 from qibotn.backends.cpu import CpuTensorNet
-from qibotn.benchmark_cases import build_circuit as build_benchmark_circuit
+from qibotn.benchmark_cases import (
+    build_circuit as build_benchmark_circuit,
+    exact_pauli_sum,
+)
 
 
 def build_circuit(nqubits=6):
@@ -109,6 +112,59 @@ def test_cpu_mps_sampling_uses_nshots():
     assert set(result.frequencies()) <= {"0000", "1111"}
 
 
+def test_cpu_mps_mpo_expectation_matches_statevector():
+    circuit = build_circuit(nqubits=4)
+    x = np.array([[0, 1], [1, 0]], dtype=complex)
+    z = np.array([[1, 0], [0, -1]], dtype=complex)
+    i2 = np.eye(2, dtype=complex)
+    mpo = [
+        x.reshape(1, 2, 2, 1),
+        z.reshape(1, 2, 2, 1),
+        i2.reshape(1, 2, 2, 1),
+        i2.reshape(1, 2, 2, 1),
+    ]
+    exact = exact_pauli_sum(circuit, [(1.0, (("X", 0), ("Z", 1)))], 4)
+
+    backend = CpuTensorNet(
+        {
+            "MPI_enabled": False,
+            "MPS_enabled": True,
+            "NCCL_enabled": False,
+            "expectation_enabled": {"mpo_tensors": mpo},
+            "max_bond_dimension": 64,
+            "tensor_module": "torch",
+            "torch_threads": 1,
+        }
+    )
+    value = backend.execute_circuit(circuit)[0]
+
+    assert math.isclose(value, exact, abs_tol=1e-12)
+
+
+def test_cpu_mps_dense_observable_dict_matches_known_value():
+    circuit = Circuit(2)
+    circuit.add(gates.H(0))
+    circuit.add(gates.CNOT(0, 1))
+
+    bell = np.zeros((4, 4), dtype=complex)
+    bell[0, 0] = bell[0, 3] = bell[3, 0] = bell[3, 3] = 0.5
+
+    backend = CpuTensorNet(
+        {
+            "MPI_enabled": False,
+            "MPS_enabled": True,
+            "NCCL_enabled": False,
+            "expectation_enabled": {"matrix": bell, "qubits": [0, 1]},
+            "max_bond_dimension": 16,
+            "tensor_module": "torch",
+            "torch_threads": 1,
+        }
+    )
+    value = backend.execute_circuit(circuit)[0]
+
+    assert math.isclose(value, 1.0, abs_tol=1e-12)
+
+
 def test_cpu_generic_tn_long_pauli_string_matches_statevector():
     circuit = build_benchmark_circuit("rxx_rzz", 10, 2, 42)
     observable = {"pauli_string_pattern": "XZ"}