diff --git a/src/qibo/quantum_info/metrics.py b/src/qibo/quantum_info/metrics.py
index c320d99ffb..6a4cd9b970 100644
--- a/src/qibo/quantum_info/metrics.py
+++ b/src/qibo/quantum_info/metrics.py
@@ -891,26 +891,26 @@ def quantum_fisher_information_matrix(
 
     if parameters is None:
         parameters = circuit.get_parameters()
-        parameters = backend.cast(parameters, dtype=float)
+        parameters = backend.cast(parameters, dtype=float).flatten()
 
     jacobian = backend.calculate_jacobian_matrix(
         circuit, parameters, initial_state, return_complex
     )
-    jacobian = (
-        jacobian[0] + 1j * jacobian[1]
-        if return_complex
-        else backend.cast(jacobian, dtype=np.complex128)
-    )
+
+    if return_complex:
+        jacobian = jacobian[0] + 1j * jacobian[1]
+
+    jacobian = backend.cast(jacobian, dtype=np.complex128)
 
     copied = circuit.copy(deep=True)
     copied.set_parameters(parameters)
 
     state = backend.execute_circuit(copied, initial_state=initial_state).state()
-
-    overlaps = backend.np.conj(state.T) @ jacobian
+    print(state.dtype, jacobian.dtype)
+    overlaps = jacobian.T @ state
 
     qfim = jacobian.T @ jacobian
-    qfim = qfim - backend.np.outer(backend.np.conj(overlaps.T), overlaps)
+    qfim = qfim - backend.np.outer(overlaps, backend.np.conj(overlaps.T))
 
     return 4 * backend.np.real(qfim)
 
diff --git a/tests/test_quantum_info_metrics.py b/tests/test_quantum_info_metrics.py
index 93d5027cbe..3187f1ea6f 100644
--- a/tests/test_quantum_info_metrics.py
+++ b/tests/test_quantum_info_metrics.py
@@ -390,9 +390,10 @@ def test_frame_potential(backend, nqubits, power_t, samples):
     backend.assert_allclose(potential, potential_haar, rtol=1e-2, atol=1e-2)
 
 
+@pytest.mark.parametrize("params_flag", [None, True])
 @pytest.mark.parametrize("return_complex", [False, True])
 @pytest.mark.parametrize("nqubits", [4, 8])
-def test_qfim(backend, nqubits, return_complex):
+def test_qfim(backend, nqubits, return_complex, params_flag):
     if backend.name not in ["pytorch", "tensorflow"]:
         circuit = Circuit(nqubits)
         params = np.random.rand(3)
@@ -411,14 +412,19 @@ def test_qfim(backend, nqubits, return_complex):
         for param in params[:-1]:
             elem = float(target[-1] * backend.np.sin(param) ** 2)
             target.append(elem)
-        target = 4 * backend.np.diag(backend.cast(target))
+        target = 4 * backend.np.diag(backend.cast(target, dtype=np.float64))
 
         # numerical qfim from quantum_info
         circuit = unary_encoder(data, "diagonal")
-        circuit.set_parameters(params)
+
+        if params_flag is not None:
+            circuit.set_parameters(params)
+        else:
+            params = params_flag
 
         qfim = quantum_fisher_information_matrix(
             circuit, params, return_complex=return_complex, backend=backend
         )
+        # qfim = backend.cast(qfim, dtype=np.float64)
 
-        backend.assert_allclose(qfim, target, atol=1e-10)
+        backend.assert_allclose(qfim, target, atol=1e-6)