IBMQ probs test (#82)

* Adding an IBMQ probability test * Changing to PL-Qiskit tol fixture * Removing commented out line, updating docstring * CHANGELOG Co-authored-by: Josh Izaac <[email protected]>
PennyLaneAI · Apr 15, 2020 · 899b606 · 899b606
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,23 +4,37 @@
 
 ### Breaking changes
 
+* Now supports Qiskit version 0.18.0. As a result of breaking changes
+  within Qiskit, version 0.17 and below are no longer supported.
+  [(#81)](https://github.com/XanaduAI/pennylane-qiskit/pull/81)
+
 ### Improvements
 
+* Added a test for returning probabilities when using the `IBMQDevice`.
+  [(#82)](https://github.com/XanaduAI/pennylane-qiskit/pull/82)
+
 ### Documentation
 
 * Major redesign of the documentation, making it easier to navigate.
   [(#78)](https://github.com/XanaduAI/pennylane-qiskit/pull/78)
 
 ### Bug fixes
 
-* Renamed `QiskitDevice.probabilities` to `QiskitDevice.probability` to overload `pennylane.Device.probability`. This fixes a bug that raises `NotImplementedError` when a QNode is used to compute probabilities on a IBMQ device.
- [(#80)](https://github.com/XanaduAI/pennylane-qiskit/pull/80)
+* Added a type conversion of parameters for parametrized gates, and renamed
+  various gates for Qiskit version 0.18.0 support.
+  [(#81)](https://github.com/XanaduAI/pennylane-qiskit/pull/81)
+
+* Renamed `QiskitDevice.probabilities` to `QiskitDevice.probability` to overload
+  `pennylane.Device.probability`. This fixes a bug that raises `NotImplementedError`
+  when a QNode is used to compute probabilities on a IBMQ device.
+  [(#80)](https://github.com/XanaduAI/pennylane-qiskit/pull/80)
+
 
 ### Contributors
 
 This release contains contributions from (in alphabetical order):
 
-Rafael Haenel
+Rafael Haenel, Josh Izaac, Maria Schuld, Antal Száva
 
 ---
 

diff --git a/tests/test_ibmq.py b/tests/test_ibmq.py
@@ -140,3 +140,28 @@ def circuit(theta, phi):
     res = circuit(theta, phi)
     expected = np.array([np.cos(theta), np.cos(theta) * np.cos(phi)])
     assert np.allclose(res, expected, **tol)
+
+
+@pytest.mark.parametrize("analytic", [False])
+@pytest.mark.parametrize("x", [[0.2, 0.5], [0.4, 0.9], [0.8, 0.3]])
+@pytest.mark.parametrize("shots", [1000])
+def test_probability(token, x, tol, shots):
+    """Test that the probs function works."""
+    IBMQ.enable_account(token)
+    dev = IBMQDevice(wires=2, backend="ibmq_qasm_simulator", shots=shots)
+    dev_analytic = qml.device("default.qubit", wires=2, analytic=True)
+
+    def circuit(x):
+        qml.RX(x[0], wires=0)
+        qml.RY(x[1], wires=0)
+        qml.CNOT(wires=[0, 1])
+        return qml.probs(wires=[0, 1])
+
+    prob = qml.QNode(circuit, dev)
+    prob_analytic = qml.QNode(circuit, dev_analytic)
+
+    called_prob = prob(x)
+
+    assert np.isclose(called_prob.sum(), 1, **tol)
+    assert np.allclose(prob_analytic(x), prob(x), **tol)
+    assert not np.array_equal(prob_analytic(x), prob(x))