minor fixup spex backend (#381)

* import error in spex backend
* spex-backend: error in hadamard compiling
* test_gradients: samplers/simulators missmatch

Author: kottmanj

src/tequila/simulators/simulator_spex.py

@@ -2,7 +2,8 @@
 from tequila.wavefunction.qubit_wavefunction import QubitWaveFunction
 from tequila.utils import TequilaException
 from tequila.hamiltonian import PauliString
-from tequila.circuit._gates_impl import ExponentialPauliGateImpl, QGateImpl, RotationGateImpl, QubitHamiltonian, QubitExcitationImpl
+from tequila.circuit._gates_impl import ExponentialPauliGateImpl, QGateImpl, RotationGateImpl, QubitHamiltonian
+from tequila.circuit.gates import QubitExcitationImpl
 from tequila import BitNumbering
 
 
@@ -218,15 +219,28 @@ def add_basic_gate(self, gate, circuit, *args, **kwargs):
                 self.add_basic_gate(sub_gate, circuit, *args, **kwargs)
 
         elif isinstance(gate, QGateImpl):
-            # Convert standard gates to Pauli rotations
-            for ps in gate.make_generator(include_controls=True).paulistrings:
-                angle = numpy.pi * ps.coeff
-                if self.angle_threshold is not None and abs(angle) < self.angle_threshold:
-                    continue
-                exp_term = spex_tequila.ExpPauliTerm()
-                exp_term.pauli_map = dict(ps.items())
-                exp_term.angle = angle
-                circuit.append(exp_term)
+            if gate.name.lower() in ["x","y","z"]:
+                # Convert standard gates to Pauli rotations
+                for ps in gate.make_generator(include_controls=True).paulistrings:
+                    angle = numpy.pi * ps.coeff
+                    if self.angle_threshold is not None and abs(angle) < self.angle_threshold:
+                        continue
+                    exp_term = spex_tequila.ExpPauliTerm()
+                    exp_term.pauli_map = dict(ps.items())
+                    exp_term.angle = angle
+                    circuit.append(exp_term)
+            elif gate.name.lower() in ["h", "hadamard"]:
+                assert len(gate.target)==1
+                target = gate.target[0]
+                for ps in ["-0.25*Y({q})", "Z({q})", "0.25*Y({q})"]:
+                    ps = QubitHamiltonian(ps.format(q=gate.target[0])).paulistrings[0]
+                    angle = numpy.pi * ps.coeff
+                    exp_term = spex_tequila.ExpPauliTerm()
+                    exp_term.pauli_map = dict(ps.items())
+                    exp_term.angle = angle
+                    circuit.append(exp_term)
+            else:
+                raise TequilaSpexException("{} not supported. Only x,y,z,h".format(gate.name.lower()))
 
         else:
             raise TequilaSpexException(f"Unsupported gate object type: {type(gate)}. "

tests/test_gradient.py

@@ -92,7 +92,7 @@ def test_gradient_UY_HX(simulator, angle_value, controlled, assume_real, silent=
         print("cos(angle)=", numpy.cos(angle()))
 
 
-@pytest.mark.parametrize("simulator", simulators)
+@pytest.mark.parametrize("simulator", samplers)
 @pytest.mark.parametrize("controlled", [False, True])
 @pytest.mark.parametrize("assume_real", [False, True])
 @pytest.mark.parametrize("angle_value", numpy.random.uniform(0.0, 2.0 * numpy.pi, 1))