Circuits obtained from initialize cannot be combined #433
Description
Circuits obtained by initialize cannot be combined.
Expected Behavior
Circuits generated by initialize() should behave the same with those created manually.
Circuits constructed manually can be combined with + as below:
qp = QuantumProgram()
q = qp.create_quantum_register("q", 1)
c = qp.create_classical_register("c", 1)
qc1 = qp.create_circuit("H1", [q], [c])
qc1.h(q)
qc2 = qp.create_circuit("H2", [q], [c])
qc2.x(q)
qc2.h(q)
qp.add_circuit("H1_and_H2", qc1 + qc2)
circuit_drawer(qp.get_circuit("H1_and_H2"))
This will create a concatenated circuit as in the image below:
Current Behavior
The following code generates error:
qp = QuantumProgram()
q = qp.create_quantum_register("q", 1)
c = qp.create_classical_register("c", 1)
qc1Error = qp.create_circuit("H1", [q], [c])
qc1Error.initialize([1.0/np.sqrt(2), 1.0/np.sqrt(2)], [ q[0] ])
qc2Error = qp.create_circuit("H2", [q], [c])
qc2Error.initialize([1.0/np.sqrt(2), -1.0/np.sqrt(2)], [ q[0] ])
qp.add_circuit("H1_and_H2", qc1Error + qc2Error)
Note that qc1Error and qc2Error are essentially "H" and "X H" as below:
Possible Solution
No Idea. Here is the error message:
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-27-515dca717837> in <module>()
10 qc2Error.initialize([1.0/np.sqrt(2), -1.0/np.sqrt(2)], [ q[0] ])
11
---> 12 qp.add_circuit("H1_and_H2", qc1Error + qc2Error)
13
14
~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/_quantumcircuit.py in __add__(self, rhs)
142 def __add__(self, rhs):
143 """Overload + to implement self.concatenate."""
--> 144 return self.combine(rhs)
145
146 def __iadd__(self, rhs):
~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/_quantumcircuit.py in combine(self, rhs)
114 circuit = QuantumCircuit(*combined_registers)
115 for gate in itertools.chain(self.data, rhs.data):
--> 116 gate.reapply(circuit)
117 return circuit
118
~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/extensions/quantum_initializer/_initializer.py in reapply(self, circ)
101 def reapply(self, circ):
102 """Reapply this gate to the corresponding qubits in circ."""
--> 103 self._modifiers(circ.initialize(self.name, self.param, self.arg))
104
105 def gates_to_uncompute(self):
TypeError: initialize() takes 3 positional arguments but 4 were given
Steps to Reproduce (for bugs)
Context
Your Environment
- Version used:
- Environment name and version (e.g. Python 3.6.1):
- Operating System and version: