From 351eff84f19618d2720cffb13f8e6f97901103a6 Mon Sep 17 00:00:00 2001
From: MatteoRobbiati <robbiati.matteo@gmail.com>
Date: Tue, 9 Jan 2024 09:51:57 +0100
Subject: [PATCH] real expv in expectation

---
 src/qibo/hamiltonians/hamiltonians.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/qibo/hamiltonians/hamiltonians.py b/src/qibo/hamiltonians/hamiltonians.py
index 0aa68d08a6..2933163354 100644
--- a/src/qibo/hamiltonians/hamiltonians.py
+++ b/src/qibo/hamiltonians/hamiltonians.py
@@ -155,7 +155,7 @@ def expectation_from_samples(self, freq, qubit_map=None):
             for i in qubit_map:
                 index += int(k[qubit_map.index(i)]) * 2 ** (size - 1 - i)
             expval += obs[index, index] * counts[j]
-        return expval
+        return np.real(expval)
 
     def eye(self, dim: Optional[int] = None):
         """Generate Identity matrix with dimension ``dim``"""