Merge pull request #1360 from qiboteam/log_entropies

Fix value of the spectrum returned in the `quantum_info.entropies.von_neumann_entropy`
qiboteam · Jun 17, 2024 · 70901d5 · 70901d5
2 parents 0d86ec5 + 8f2d00f
commit 70901d5
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diff --git a/src/qibo/quantum_info/entropies.py b/src/qibo/quantum_info/entropies.py
@@ -461,7 +461,7 @@ def von_neumann_entropy(
 
     if purity(state) == 1.0:
         if return_spectrum:
-            return 0.0, backend.cast([1.0], dtype=float)
+            return 0.0, backend.cast([0.0], dtype=float)
 
         return 0.0
 

diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
@@ -97,7 +97,7 @@ def test_entropy_in_circuit(backend, density_matrix, base):
     values = [backend.to_numpy(x) for x in entropy]
     backend.assert_allclose(values, target, atol=PRECISION_TOL)
 
-    target_spectrum = [1.0] + list([0, 0, np.log(2), np.log(2)] / np.log(base))
+    target_spectrum = [0.0] + list([0, 0, np.log(2), np.log(2)] / np.log(base))
     entropy_spectrum = np.ravel(np.concatenate(entropy.spectrum)).tolist()
     backend.assert_allclose(entropy_spectrum, target_spectrum, atol=PRECISION_TOL)