updating qiskit noise imports to latest versions (#355)

Author: kottmanj

src/tequila/simulators/simulator_api.py

@@ -36,9 +36,12 @@
     HAS_QISKIT = True
     INSTALLED_SIMULATORS["qiskit"] = BackendTypes(BackendCircuitQiskit, BackendExpectationValueQiskit)
     INSTALLED_SAMPLERS["qiskit"] = BackendTypes(BackendCircuitQiskit, BackendExpectationValueQiskit)
-    INSTALLED_NOISE_SAMPLERS["qiskit"] = BackendTypes(BackendCircuitQiskit, BackendExpectationValueQiskit)
+    from tequila.simulators.simulator_qiskit import HAS_NOISE as HAS_QISKIT_NOISE
+    if HAS_QISKIT_NOISE:
+        INSTALLED_NOISE_SAMPLERS["qiskit"] = BackendTypes(BackendCircuitQiskit, BackendExpectationValueQiskit)
 except ImportError:
     HAS_QISKIT = False
+    HAS_QISKIT_NOISE = False
 
 HAS_QIBO = True
 try:
@@ -133,6 +136,8 @@ def show_available_simulators():
                                                              str(k in INSTALLED_SAMPLERS),
                                                              str(k in INSTALLED_NOISE_SAMPLERS),
                                                              str(k in INSTALLED_BACKENDS)))
+    if HAS_QISKIT and not HAS_QISKIT_NOISE:
+        print("missing qiskit_aer: no noisy simulation")
 
 
 def pick_backend(backend: str = None, samples: int = None, noise: NoiseModel = None, device=None,

src/tequila/simulators/simulator_qiskit.py

@@ -3,12 +3,20 @@
 from tequila import TequilaException, TequilaWarning
 from tequila import BitString, BitNumbering, BitStringLSB
 from tequila.utils.keymap import KeyMapRegisterToSubregister
-import qiskit, numpy, warnings
-import qiskit.providers.aer.noise as qiskitnoise
 from tequila.utils import to_float
-import qiskit.test.mock.backends
-from qiskit.providers.ibmq import IBMQBackend
+import qiskit, numpy, warnings
 
+HAS_NOISE=True
+try:
+    from qiskit_aer import noise as qiskitnoise
+except:
+    HAS_NOISE = False
+
+HAS_IBMQ=True
+try:
+    from qiskit.providers.ibmq import IBMQBackend
+except:
+    HAS_IBMQ=False
 
 def get_bit_flip(p):
     """