Add test for expectation and updates

tests/test_cuquantum_cutensor_backend.py

@@ -1,11 +1,13 @@
 from timeit import default_timer as timer
 
-import config
 import cupy as cp
 import numpy as np
 import pytest
 import qibo
 from qibo.models import QFT
+from qibo import Circuit, gates, hamiltonians, construct_backend
+from qibo.symbols import X, Z
+import math
 
 
 def qibo_qft(nqubits, swaps):
@@ -22,6 +24,16 @@ def time(func):
     return time, res
 
 
+def build_observable(nqubits):
+    """Helper function to construct a target observable."""
+    hamiltonian_form = 0
+    for i in range(nqubits):
+        hamiltonian_form += 0.5 * X(i % nqubits) * Z((i + 1) % nqubits)
+
+    hamiltonian = hamiltonians.SymbolicHamiltonian(form=hamiltonian_form)
+    return hamiltonian, hamiltonian_form
+
+
 @pytest.mark.gpu
 @pytest.mark.parametrize("nqubits", [1, 2, 5, 10])
 def test_eval(nqubits: int, dtype="complex128"):
@@ -35,16 +47,19 @@ def test_eval(nqubits: int, dtype="complex128"):
     import qibotn.eval
 
     # Test qibo
-    qibo.set_backend(backend=config.qibo.backend, platform=config.qibo.platform)
+    # qibo.set_backend(backend=config.qibo.backend, platform=config.qibo.platform)
+    qibo.set_backend(backend="numpy")
     qibo_time, (qibo_circ, result_sv) = time(lambda: qibo_qft(nqubits, swaps=True))
+    result_sv_cp = cp.asarray(result_sv)
 
     # Test Cuquantum
     cutn_time, result_tn = time(
         lambda: qibotn.eval.dense_vector_tn(qibo_circ, dtype).flatten()
     )
 
-    assert 1e-2 * qibo_time < cutn_time < 1e2 * qibo_time
-    assert np.allclose(result_sv, result_tn), "Resulting dense vectors do not match"
+    print(f"State vector difference: {abs(result_tn - result_sv_cp).max():0.3e}")
+
+    assert cp.allclose(result_sv_cp, result_tn), "Resulting dense vectors do not match"
 
 
 @pytest.mark.gpu
@@ -60,7 +75,7 @@ def test_mps(nqubits: int, dtype="complex128"):
     import qibotn.eval
 
     # Test qibo
-    qibo.set_backend(backend=config.qibo.backend, platform=config.qibo.platform)
+    qibo.set_backend(backend="numpy")
 
     qibo_time, (circ_qibo, result_sv) = time(lambda: qibo_qft(nqubits, swaps=True))
 
@@ -81,4 +96,24 @@ def test_mps(nqubits: int, dtype="complex128"):
 
     print(f"State vector difference: {abs(result_tn - result_sv_cp).max():0.3e}")
 
-    assert cp.allclose(result_tn, result_sv_cp)
+    assert cp.allclose(result_tn, result_sv_cp), "Resulting dense vectors do not match"
+
+
+@pytest.mark.gpu
+@pytest.mark.parametrize("nqubits", [2, 5, 10])
+def test_expectation(nqubits: int, dtype="complex128"):
+    import qibotn.eval
+
+    circ_qibo, state_vec_qibo = qibo_qft(nqubits, swaps=True)
+    ham, ham_form = build_observable(nqubits)
+
+    numpy_backend = construct_backend("numpy")
+    exact_expval = numpy_backend.calculate_expectation_state(
+        hamiltonian=ham,
+        state=state_vec_qibo,
+        normalize=False,
+    )
+
+    tn_expval = qibotn.eval.expectation_tn(circ_qibo, dtype, ham).flatten()
+
+    assert math.isclose(exact_expval.item(), tn_expval.real.get().item(), abs_tol=1e-7)