Remove clbits from QuantumNeuralNetwork class (#63)

* remove clbits as sampler primitive cannot take clbits during training

* remove classical register from tests

Author: SaashaJoshi

piqture/neural_networks/quantum_neural_network.py

@@ -39,9 +39,10 @@ def __init__(self, num_qubits: int):
             raise ValueError("The input num_qubits must be at least 1.")
 
         self.num_qubits = num_qubits
-        self._circuit = QuantumCircuit(self.num_qubits, self.num_qubits)
+        self._circuit = QuantumCircuit(self.num_qubits)
         self.qr = self._circuit.qubits
-        self.cr = self._circuit.clbits
+        # Remove clbits as Sampler cannot take clbits.
+        # self.cr = self._circuit.clbits
 
     @property
     def circuit(self):

tests/neural_networks/test_qcnn.py

@@ -44,7 +44,7 @@ def test_value_num_qubits(self, num_qubits):
     def test_circuit_property(self, num_qubits):
         """Tests the QCNN circuit."""
         qcnn = QCNN(num_qubits)
-        assert qcnn.circuit == QuantumCircuit(num_qubits, num_qubits)
+        assert qcnn.circuit == QuantumCircuit(num_qubits)
 
     @pytest.mark.parametrize(
         "num_qubits, operations",