赛前稳定版

tests/test_vidal_backend.py

@@ -2,10 +2,18 @@ import math
 
 import numpy as np
 from qibo import Circuit, gates, hamiltonians
-from qibo.symbols import X, Y, Z
+from qibo.symbols import Symbol, X, Y, Z
 
-from qibotn.backends.vidal import VidalBackend, _can_route_non_adjacent, _unsupported_reason
+from qibotn.benchmark_cases import exact_pauli_sum
+from qibotn.backends.vidal import (
+    VidalBackend,
+    _can_route_non_adjacent,
+    _unsupported_reason,
+    _operator_terms_to_mpo,
+    _symbolic_hamiltonian_to_operator_terms,
+)
 from qibotn.backends.vidal_tebd import (
+    VidalTEBDExecutor,
     _route_non_adjacent_gates,
     _gate_sites,
 )
@@ -37,6 +45,25 @@ def test_vidal_backend_expectation_matches_statevector():
     np.testing.assert_allclose(value, exact, atol=1e-12)
 
 
+def test_vidal_backend_accepts_unlimited_bond_and_no_cutoff():
+    circuit = build_local_circuit(nqubits=6, nlayers=2)
+    observable = hamiltonians.SymbolicHamiltonian(
+        form=0.5 * X(0) * Z(1) - 0.7 * Z(5)
+    )
+    exact = observable.expectation_from_state(circuit().state(numpy=True))
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=None,
+        cut_ratio=None,
+        tensor_module="torch",
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=False)
+
+    np.testing.assert_allclose(value, exact, atol=1e-12)
+
+
 def test_vidal_backend_fallback_for_non_adjacent_gate():
     """compile_circuit=False (default) → falls back to qmatchatea for non-adjacent."""
     circuit = Circuit(4)
@@ -128,6 +155,208 @@ def test_routing_non_adjacent_cnot():
     np.testing.assert_allclose(value, exact, atol=1e-12)
 
 
+def test_routing_preserves_reversed_non_adjacent_gate_order():
+    circuit = Circuit(6)
+    circuit.add(gates.X(5))
+    circuit.add(gates.H(0))
+    circuit.add(gates.CNOT(5, 0))
+
+    observable = hamiltonians.SymbolicHamiltonian(form=X(0) + Z(5) + Z(0) * Z(5))
+    exact = observable.expectation_from_state(circuit().state(numpy=True))
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=64,
+        tensor_module="torch",
+        compile_circuit=True,
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=False)
+
+    np.testing.assert_allclose(value, exact, atol=1e-12)
+
+
+def test_vidal_backend_preprocesses_non_adjacent_circuit():
+    circuit = Circuit(4)
+    circuit.add(gates.H(0))
+    circuit.add(gates.CNOT(0, 3))
+    observable = hamiltonians.SymbolicHamiltonian(form=Z(0) * Z(3))
+    exact = observable.expectation_from_state(circuit().state(numpy=True))
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=64,
+        tensor_module="torch",
+        compile_circuit=True,
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=True)
+
+    np.testing.assert_allclose(value, exact, atol=1e-12)
+
+
+def test_vidal_backend_preprocesses_toffoli_locally():
+    circuit = Circuit(4)
+    circuit.add(gates.H(0))
+    circuit.add(gates.H(1))
+    circuit.add(gates.TOFFOLI(0, 1, 3))
+    observable = hamiltonians.SymbolicHamiltonian(form=Z(0) * Z(3))
+    exact = observable.expectation_from_state(circuit().state(numpy=True))
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=128,
+        tensor_module="torch",
+        compile_circuit=True,
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=True)
+
+    np.testing.assert_allclose(value, exact, atol=1e-12)
+
+
+def test_vidal_expectation_preserves_complex_coefficients():
+    circuit = Circuit(1)
+    observable = hamiltonians.SymbolicHamiltonian(form=(1.0 + 2.0j) * Z(0))
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=8,
+        tensor_module="torch",
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=False)
+
+    np.testing.assert_allclose(value, 1.0 + 2.0j, atol=1e-12)
+
+
+def test_vidal_expectation_supports_custom_local_symbols():
+    circuit = build_local_circuit(nqubits=4, nlayers=2)
+    a0 = Symbol(0, np.array([[0.2, 1.0], [1.0, -0.3]], dtype=complex), name="A")
+    b2 = Symbol(2, np.array([[0.7, -0.4j], [0.4j, 0.1]], dtype=complex), name="B")
+    a3 = Symbol(3, np.array([[0.5, 0.2], [0.2, -0.8]], dtype=complex), name="A")
+    observable = hamiltonians.SymbolicHamiltonian(form=0.7 * a0 * b2 - 0.4 * a3)
+    exact = observable.expectation_from_state(circuit().state(numpy=True))
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=64,
+        tensor_module="torch",
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=False)
+
+    np.testing.assert_allclose(value, exact, atol=1e-12)
+
+
+def test_vidal_executor_mpo_expectation_matches_pauli_sum():
+    circuit = build_local_circuit(nqubits=4, nlayers=2)
+    executor = VidalTEBDExecutor(
+        nqubits=circuit.nqubits,
+        max_bond=64,
+        tensor_module="torch",
+    )
+    executor.run_circuit(circuit)
+
+    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),
+    ]
+    mpo_value = executor.expectation_mpo(mpo)
+    pauli_value = executor.expectation_pauli_sum([(1.0, (("X", 0), ("Z", 1)))])
+
+    np.testing.assert_allclose(mpo_value, pauli_value, atol=1e-12)
+
+
+def test_vidal_backend_accepts_mpo_observable_dict():
+    circuit = build_local_circuit(nqubits=4, nlayers=2)
+    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 = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=64,
+        tensor_module="torch",
+        fallback=False,
+    )
+    value = backend.expectation(circuit, {"mpo_tensors": mpo}, preprocess=False)
+
+    np.testing.assert_allclose(value, exact, atol=1e-12)
+
+
+def test_vidal_symbolic_hamiltonian_auto_mpo_matches_operator_sum():
+    circuit = build_local_circuit(nqubits=5, nlayers=2)
+    observable = hamiltonians.SymbolicHamiltonian(
+        form=0.3 * X(0) * Z(1) - 0.2j * Y(2) + 0.7 * Z(3) * X(4)
+    )
+
+    executor = VidalTEBDExecutor(
+        nqubits=circuit.nqubits,
+        max_bond=64,
+        tensor_module="torch",
+    )
+    executor.run_circuit(circuit)
+    terms = _symbolic_hamiltonian_to_operator_terms(observable)
+
+    term_value = executor.expectation_operator_sum(terms)
+    mpo_value = executor.expectation_mpo(_operator_terms_to_mpo(terms, circuit.nqubits))
+
+    np.testing.assert_allclose(mpo_value, term_value, atol=1e-12)
+
+
+def test_vidal_backend_accepts_dense_two_qubit_observable():
+    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
+    observable = {"matrix": bell, "qubits": [0, 1]}
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=16,
+        tensor_module="torch",
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=False)
+
+    np.testing.assert_allclose(value, 1.0, atol=1e-12)
+
+
+def test_vidal_backend_dense_observable_preserves_complex_value():
+    circuit = Circuit(2)
+    circuit.add(gates.H(0))
+    circuit.add(gates.H(1))
+
+    op = np.zeros((4, 4), dtype=complex)
+    op[0, 3] = 1.0
+    observable = {"coefficient": 1.0j, "matrix": op, "qubits": [0, 1]}
+
+    backend = VidalBackend()
+    backend.configure_tn_simulation(
+        max_bond_dimension=16,
+        tensor_module="torch",
+        fallback=False,
+    )
+    value = backend.expectation(circuit, observable, preprocess=False)
+
+    np.testing.assert_allclose(value, 0.25j, atol=1e-12)
+
+
 def test_truncation_error_no_truncation():
     """With large bond, truncation error should be essentially zero."""
     circuit = build_local_circuit(nqubits=6, nlayers=2)
@@ -141,6 +370,10 @@ def test_truncation_error_no_truncation():
     assert backend.last_truncation_error < 1e-14, (
         f"Expected near-zero truncation error, got {backend.last_truncation_error}"
     )
+    assert backend.last_max_truncation_error < 1e-14, (
+        "Expected near-zero max truncation error, got "
+        f"{backend.last_max_truncation_error}"
+    )
 
 
 def test_vidal_backend_matches_statevector_multiterm():