Fix stuff related to I terms

qiboteam · Dec 17, 2024 · 2ce694e · 2ce694e
1 parent 201812e
commit 2ce694e
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Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/src/qibo/hamiltonians/hamiltonians.py b/src/qibo/hamiltonians/hamiltonians.py
@@ -587,7 +587,13 @@ def expectation_from_circuit(self, circuit: "Circuit", nshots: int = 1000) -> fl
             # build diagonal observable
             Z_observables.append(
                 SymbolicHamiltonian(
-                    prod([Z(q) for q in term.target_qubits]),
+                    prod(
+                        [
+                            Z(factor.target_qubit)
+                            for factor in term.factors
+                            if factor.name[0] != "I"
+                        ]
+                    ),
                     nqubits=circuit.nqubits,
                     backend=self.backend,
                 )
@@ -649,7 +655,9 @@ def expectation_from_samples(self, freq: dict, qubit_map: list = None) -> float:
         )
         expvals = []
         for term in self.terms:
-            qubits = term.target_qubits
+            qubits = {
+                factor.target_qubit for factor in term.factors if factor.name[0] != "I"
+            }
             expvals.extend(
                 [
                     term.coefficient.real

diff --git a/tests/test_hamiltonians.py b/tests/test_hamiltonians.py
@@ -295,7 +295,7 @@ def test_hamiltonian_expectation_from_circuit(backend):
     backend.set_seed(12)
 
     nshots = 4 * 10**6
-    observable = I(0) + X(0) * Z(1) + Y(0) * X(2) / 2 - Z(0) * (1 - Y(1)) ** 3
+    observable = I(0) * Z(1) + X(0) * Z(1) + Y(0) * X(2) / 2 - Z(0) * (1 - Y(1)) ** 3
     exp, H, c = non_exact_expectation_test_setup(backend, observable)
     exp_from_samples = H.expectation_from_circuit(c, nshots=nshots)
     backend.assert_allclose(exp, exp_from_samples, atol=1e-2)