Add Harmony backend for IonQ

pennylane_ionq/__init__.py

@@ -15,5 +15,5 @@
 PennyLane IonQ overview
 =======================
 """
-from .device import SimulatorDevice, QPUDevice
+from .device import SimulatorDevice, QPUDevice, HarmonyDevice
 from ._version import __version__

pennylane_ionq/api_client.py

@@ -117,7 +117,9 @@ class APIClient:
     BASE_URL = "https://{}".format(HOSTNAME)
 
     def __init__(self, **kwargs):
-        self.AUTHENTICATION_TOKEN = os.getenv("IONQ_API_KEY") or kwargs.get("api_key", None)
+        self.AUTHENTICATION_TOKEN = os.getenv("IONQ_API_KEY") or kwargs.get(
+            "api_key", None
+        )
         self.DEBUG = False
 
         if "IONQ_DEBUG" in os.environ:
@@ -220,7 +222,9 @@ def post(self, path, payload):
         Returns:
             requests.Response: A response object, or None if no response could be fetched
         """
-        return self.request(requests.post, url=self.join_path(path), data=json.dumps(payload))
+        return self.request(
+            requests.post, url=self.join_path(path), data=json.dumps(payload)
+        )
 
 
 class ResourceManager:
@@ -259,7 +263,9 @@ def get(self, resource_id=None):
             resource_id (int): the ID of an object to be retrieved
         """
         if "GET" not in self.resource.SUPPORTED_METHODS:
-            raise MethodNotSupportedException("GET method on this resource is not supported")
+            raise MethodNotSupportedException(
+                "GET method on this resource is not supported"
+            )
 
         if resource_id is not None:
             response = self.client.get(self.join_path(str(resource_id)))
@@ -276,7 +282,9 @@ def create(self, **params):
             **params: arbitrary parameters to be passed on to the POST request
         """
         if "POST" not in self.resource.SUPPORTED_METHODS:
-            raise MethodNotSupportedException("POST method on this resource is not supported")
+            raise MethodNotSupportedException(
+                "POST method on this resource is not supported"
+            )
 
         if self.resource.id:
             raise ObjectAlreadyCreatedException("ID must be None when calling create")

pennylane_ionq/device.py

@@ -83,7 +83,9 @@ class IonQDevice(QubitDevice):
 
     def __init__(self, wires, *, target="simulator", shots=1024, api_key=None):
         if shots is None:
-            raise ValueError("The ionq device does not support analytic expectation values.")
+            raise ValueError(
+                "The ionq device does not support analytic expectation values."
+            )
 
         super().__init__(wires=wires, shots=shots)
         self.target = target
@@ -116,7 +118,9 @@ def apply(self, operations, **kwargs):
         rotations = kwargs.pop("rotations", [])
 
         if len(operations) == 0 and len(rotations) == 0:
-            warnings.warn("Circuit is empty. Empty circuits return failures. Submitting anyway.")
+            warnings.warn(
+                "Circuit is empty. Empty circuits return failures. Submitting anyway."
+            )
 
         for i, operation in enumerate(operations):
             if i > 0 and operation.name in {"BasisState", "QubitStateVector"}:
@@ -188,7 +192,8 @@ def prob(self):
             # Here, we rearrange the states to match the big-endian ordering
             # expected by PennyLane.
             basis_states = (
-                int(bin(int(k))[2:].rjust(self.num_wires, "0")[::-1], 2) for k in self.histogram
+                int(bin(int(k))[2:].rjust(self.num_wires, "0")[::-1], 2)
+                for k in self.histogram
             )
             idx = np.fromiter(basis_states, dtype=int)
 
@@ -204,7 +209,9 @@ def probability(self, wires=None, shot_range=None, bin_size=None):
         if shot_range is None and bin_size is None:
             return self.marginal_prob(self.prob, wires)
 
-        return self.estimate_probability(wires=wires, shot_range=shot_range, bin_size=bin_size)
+        return self.estimate_probability(
+            wires=wires, shot_range=shot_range, bin_size=bin_size
+        )
 
 
 class SimulatorDevice(IonQDevice):
@@ -234,6 +241,7 @@ def generate_samples(self):
         return QubitDevice.states_to_binary(samples, self.num_wires)
 
 
+# deprecated("Prefer HarmonyDevice to fully specify generation.")
 class QPUDevice(IonQDevice):
     r"""QPU device for IonQ.
 
@@ -263,8 +271,33 @@ def generate_samples(self):
         """
         number_of_states = 2**self.num_wires
         counts = np.rint(
-            self.prob * self.shots, out=np.zeros(number_of_states, dtype=int), casting="unsafe"
+            self.prob * self.shots,
+            out=np.zeros(number_of_states, dtype=int),
+            casting="unsafe",
         )
         samples = np.repeat(np.arange(number_of_states), counts)
         np.random.shuffle(samples)
         return QubitDevice.states_to_binary(samples, self.num_wires)
+
+
+class HarmonyDevice(QPUDevice):
+    r"""Harmony QPU device for IonQ.
+
+    Args:
+        wires (int or Iterable[Number, str]]): Number of wires to initialize the device with,
+            or iterable that contains unique labels for the subsystems as numbers (i.e., ``[-1, 0, 2]``)
+            or strings (``['ancilla', 'q1', 'q2']``).
+        shots (int, list[int]): Number of circuit evaluations/random samples used to estimate
+            expectation values of observables. If ``None``, the device calculates probability, expectation values,
+            and variances analytically. If an integer, it specifies the number of samples to estimate these quantities.
+            If a list of integers is passed, the circuit evaluations are batched over the list of shots.
+        api_key (str): The IonQ API key. If not provided, the environment
+            variable ``IONQ_API_KEY`` is used.
+    """
+    name = "IonQ QPU PennyLane plugin"
+    short_name = "ionq.qpu.harmony"
+
+    def __init__(self, wires, *, shots=1024, api_key=None):
+        super().__init__(
+            wires=wires, target="qpu.harmony", shots=shots, api_key=api_key
+        )

tests/test_device.py

@@ -96,10 +96,11 @@ def test_failedcircuit(self, monkeypatch):
             requests, "post", lambda url, timeout, data, headers: (url, data, headers)
         )
         monkeypatch.setattr(ResourceManager, "handle_response", lambda self, response: None)
+        monkeypatch.setattr(Job, "reload", lambda ignored: None)
         monkeypatch.setattr(Job, "is_complete", False)
         monkeypatch.setattr(Job, "is_failed", True)
-
-        dev = IonQDevice(wires=(0,))
+        
+        dev = IonQDevice(wires=(0,), api_key="foo")
         with pytest.raises(JobExecutionError):
             dev._submit_job()