From 2b34b5cd0ec2bbdda3e3840a79def3a3eddec822 Mon Sep 17 00:00:00 2001
From: BrunoLiegiBastonLiegi <andreapapaluca@gmail.com>
Date: Wed, 16 Oct 2024 17:32:30 +0200
Subject: [PATCH] feat: added support for power elevation + removed outdated
 test

---
 src/qibo/hamiltonians/hamiltonians.py |  5 +----
 tests/test_hamiltonians.py            |  5 ++++-
 tests/test_hamiltonians_symbolic.py   | 10 ----------
 3 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/src/qibo/hamiltonians/hamiltonians.py b/src/qibo/hamiltonians/hamiltonians.py
index a7328041b2..df1a85b4d6 100644
--- a/src/qibo/hamiltonians/hamiltonians.py
+++ b/src/qibo/hamiltonians/hamiltonians.py
@@ -585,7 +585,7 @@ def _exp_from_circuit(self, circuit: dict, qubit_map: dict, nshots: int = None):
             )
             measurements = [
                 gates.M(factor.target_qubit, basis=factor.gate.__class__)
-                for factor in term.factors
+                for factor in set(term.factors)
             ]
             circ_copy = circuit.copy(True)
             [circ_copy.add(m) for m in measurements]
@@ -672,9 +672,6 @@ def expectation_from_samples(
         Returns:
             (float) the computed expectation value.
         """
-        for term in self.terms:
-            if len(term.factors) != len(set(term.factors)):
-                raise_error(NotImplementedError, "Z^k is not implemented since Z^2=I.")
 
         if isinstance(data, dict):
             return self._exp_from_freq(data, qubit_map)
diff --git a/tests/test_hamiltonians.py b/tests/test_hamiltonians.py
index 1f02f642e7..4bdf6cbd03 100644
--- a/tests/test_hamiltonians.py
+++ b/tests/test_hamiltonians.py
@@ -264,7 +264,10 @@ def test_hamiltonian_expectation_errors(backend):
 
 @pytest.mark.parametrize(
     "observable",
-    [2 * Z(0) * Z(1) + Z(0) * Z(2), X(0) * Z(1) + Y(0) * X(2) / 2 - Z(0) * Y(1)],
+    [
+        2 * Z(0) * Z(1) ** 2 + Z(0) * Z(2),
+        X(0) * Z(1) + Y(0) * X(2) / 2 - Z(0) * Y(1) ** 3,
+    ],
 )
 def test_hamiltonian_expectation_from_samples(backend, observable):
     """Test Hamiltonian expectation value calculation."""
diff --git a/tests/test_hamiltonians_symbolic.py b/tests/test_hamiltonians_symbolic.py
index 54d8dac2e3..d1d8485703 100644
--- a/tests/test_hamiltonians_symbolic.py
+++ b/tests/test_hamiltonians_symbolic.py
@@ -330,16 +330,6 @@ def test_hamiltonian_expectation_from_samples(backend):
     backend.assert_allclose(ev0, ev1, atol=20 / np.sqrt(nshots))
 
 
-def test_hamiltonian_expectation_from_samples_errors(backend):
-    obs = [Z(0) * Y(1), Z(0) * Z(1) ** 3]
-    h1 = hamiltonians.SymbolicHamiltonian(obs[0], backend=backend)
-    h2 = hamiltonians.SymbolicHamiltonian(obs[1], backend=backend)
-    with pytest.raises(NotImplementedError):
-        h1.expectation_from_samples(None, qubit_map=None)
-    with pytest.raises(NotImplementedError):
-        h2.expectation_from_samples(None, qubit_map=None)
-
-
 @pytest.mark.parametrize("density_matrix", [False, True])
 @pytest.mark.parametrize("calcterms", [False, True])
 def test_symbolic_hamiltonian_abstract_symbol_ev(backend, density_matrix, calcterms):