change Instruction.definition from List[Tuple] to QuantumCircuit

qiskit/circuit/add_control.py

@@ -112,18 +112,18 @@ def control(operation: Union[Gate, ControlledGate],
             operation.base_gate.name == 'x'):
         qc.mct(q_control[:] + q_target[:-1], q_target[-1], q_ancillae)
     elif operation.name == 'rx':
-        qc.mcrx(operation.definition[0][0].params[0], q_control, q_target[0],
+        qc.mcrx(operation.definition.data[0][0].params[0], q_control, q_target[0],
                 use_basis_gates=True)
     elif operation.name == 'ry':
-        qc.mcry(operation.definition[0][0].params[0], q_control, q_target[0],
+        qc.mcry(operation.definition.data[0][0].params[0], q_control, q_target[0],
                 q_ancillae, mode='noancilla', use_basis_gates=True)
     elif operation.name == 'rz':
-        qc.mcrz(operation.definition[0][0].params[0], q_control, q_target[0],
+        qc.mcrz(operation.definition.data[0][0].params[0], q_control, q_target[0],
                 use_basis_gates=True)
     else:
         bgate = _unroll_gate(operation, ['u1', 'u3', 'cx'])
         # now we have a bunch of single qubit rotation gates and cx
-        for rule in bgate.definition:
+        for rule in bgate.definition.data:
             if rule[0].name == 'u3':
                 theta, phi, lamb = rule[0].params
                 if phi == -pi / 2 and lamb == pi / 2:
@@ -150,7 +150,6 @@ def control(operation: Union[Gate, ControlledGate],
             else:
                 raise CircuitError('gate contains non-controllable instructions')
 
-    instr = qc.to_instruction()
     if isinstance(operation, controlledgate.ControlledGate):
         new_num_ctrl_qubits = num_ctrl_qubits + operation.num_ctrl_qubits
         new_ctrl_state = operation.ctrl_state << num_ctrl_qubits | ctrl_state
@@ -171,11 +170,11 @@ def control(operation: Union[Gate, ControlledGate],
         ctrl_substr = ('{0}' * new_num_ctrl_qubits).format('c')
     new_name = '{0}{1}'.format(ctrl_substr, base_name)
     cgate = controlledgate.ControlledGate(new_name,
-                                          instr.num_qubits,
+                                          qc.num_qubits,
                                           operation.params,
                                           label=label,
                                           num_ctrl_qubits=new_num_ctrl_qubits,
-                                          definition=instr.definition,
+                                          definition=qc,
                                           ctrl_state=new_ctrl_state)
     cgate.base_gate = base_gate
     return cgate
@@ -185,7 +184,7 @@ def _gate_to_circuit(operation):
     qr = QuantumRegister(operation.num_qubits)
     qc = QuantumCircuit(qr, name=operation.name)
     if hasattr(operation, 'definition') and operation.definition:
-        for rule in operation.definition:
+        for rule in operation.definition.data:
             if rule[0].name in {'id', 'barrier', 'measure', 'snapshot'}:
                 raise CircuitError('Cannot make controlled gate with {} instruction'.format(
                     rule[0].name))
@@ -195,11 +194,21 @@ def _gate_to_circuit(operation):
     return qc
 
 
-def _unroll_gate(operation, basis_gates):
+def _gate_to_dag(operation):
     from qiskit.converters.circuit_to_dag import circuit_to_dag
+    if hasattr(operation, 'definition') and operation.definition:
+        return circuit_to_dag(operation.definition)
+    else:
+        qr = QuantumRegister(operation.num_qubits)
+        qc = QuantumCircuit(qr, name=operation.name)
+        qc.append(operation, qr)
+        return circuit_to_dag(qc)
+
+
+def _unroll_gate(operation, basis_gates):
     from qiskit.converters.dag_to_circuit import dag_to_circuit
     from qiskit.transpiler.passes import Unroller
     unroller = Unroller(basis_gates)
-    dag = circuit_to_dag(_gate_to_circuit(operation))
+    dag = _gate_to_dag(operation)
     qc = dag_to_circuit(unroller.run(dag))
     return qc.to_gate()

qiskit/circuit/controlledgate.py

@@ -14,13 +14,13 @@
 
 """Controlled unitary gate."""
 
-from typing import Tuple, List, Optional, Union
+from typing import List, Optional, Union
 from qiskit.circuit.exceptions import CircuitError
 
+# pylint: disable=cyclic-import
+from .quantumcircuit import QuantumCircuit
 from .gate import Gate
 from .quantumregister import QuantumRegister
-from .quantumregister import Qubit
-from .classicalregister import Clbit
 
 # pylint: disable=missing-return-doc
 
@@ -30,7 +30,7 @@ class ControlledGate(Gate):
 
     def __init__(self, name: str, num_qubits: int, params: List,
                  label: Optional[str] = None, num_ctrl_qubits: Optional[int] = 1,
-                 definition: Optional[List[Tuple[Gate, List[Qubit], List[Clbit]]]] = None,
+                 definition: Optional['QuantumCircuit'] = None,
                  ctrl_state: Optional[Union[int, str]] = None):
         """Create a new ControlledGate. In the new gate the first ``num_ctrl_qubits``
         of the gate are the controls.
@@ -90,8 +90,8 @@ def __init__(self, name: str, num_qubits: int, params: List,
         self.base_gate = None
         if definition:
             self.definition = definition
-            if len(definition) == 1:
-                base_gate = definition[0][0]
+            if len(definition.data) == 1:
+                base_gate = definition.data[0][0]
                 if isinstance(base_gate, ControlledGate):
                     self.base_gate = base_gate.base_gate
                 else:
@@ -109,25 +109,26 @@ def definition(self) -> List:
         if self._open_ctrl:
             closed_gate = self.copy()
             closed_gate.ctrl_state = None
-            # pylint: disable=cyclic-import
-            from qiskit.circuit.library.standard_gates import XGate
             bit_ctrl_state = bin(self.ctrl_state)[2:].zfill(self.num_ctrl_qubits)
             qreg = QuantumRegister(self.num_qubits, 'q')
-            definition = [(closed_gate, qreg, [])]
-            open_rules = []
+            qc_open_ctrl = QuantumCircuit(qreg)
             for qind, val in enumerate(bit_ctrl_state[::-1]):
                 if val == '0':
-                    open_rules.append([XGate(), [qreg[qind]], []])
-            if open_rules:
-                return open_rules + definition + open_rules
-            else:
-                return self._definition
+                    qc_open_ctrl.x(qind)
+            qc_open_ctrl.append(closed_gate, qargs=qreg[:])
+            for qind, val in enumerate(bit_ctrl_state[::-1]):
+                if val == '0':
+                    qc_open_ctrl.x(qind)
+            return qc_open_ctrl
         else:
             return super().definition
 
     @definition.setter
-    def definition(self, excited_def: List):
-        """Set controlled gate definition with closed controls."""
+    def definition(self, excited_def: 'QuantumCircuit'):
+        """Set controlled gate definition with closed controls.
+
+        Args:
+            excited_def: The circuit with all closed controls."""
         super(Gate, self.__class__).definition.fset(self, excited_def)
 
     @property

qiskit/circuit/instruction.py

@@ -178,7 +178,7 @@ def definition(self):
 
     @definition.setter
     def definition(self, array):
-        """Set matrix representation"""
+        """Set gate representation"""
         self._definition = array
 
     @property
@@ -246,9 +246,9 @@ def reverse_ops(self):
             return self.copy()
 
         reverse_inst = self.copy(name=self.name + '_reverse')
-        reverse_inst.definition = []
+        reverse_inst.definition.data = []
         for inst, qargs, cargs in reversed(self._definition):
-            reverse_inst._definition.append((inst.reverse_ops(), qargs, cargs))
+            reverse_inst._definition.data.append((inst.reverse_ops(), qargs, cargs))
         return reverse_inst
 
     def inverse(self):
@@ -270,9 +270,9 @@ def inverse(self):
         if self.definition is None:
             raise CircuitError("inverse() not implemented for %s." % self.name)
         inverse_gate = self.copy(name=self.name + '_dg')
-        inverse_gate._definition = []
-        for inst, qargs, cargs in reversed(self._definition):
-            inverse_gate._definition.append((inst.inverse(), qargs, cargs))
+        inverse_gate._definition.data = []
+        for inst, qargs, cargs in reversed(self._definition.data):
+            inverse_gate._definition.data.append((inst.inverse(), qargs, cargs))
         return inverse_gate
 
     def c_if(self, classical, val):
@@ -377,5 +377,14 @@ def repeat(self, n):
         qargs = [] if self.num_qubits == 0 else QuantumRegister(self.num_qubits, 'q')
         cargs = [] if self.num_clbits == 0 else ClassicalRegister(self.num_clbits, 'c')
 
-        instruction.definition = [(self, qargs[:], cargs[:])] * n
+        if instruction.definition is None:
+            # pylint: disable=cyclic-import
+            from qiskit import QuantumCircuit
+            qc = QuantumCircuit()
+            if qargs:
+                qc.add_register(qargs)
+            if cargs:
+                qc.add_register(cargs)
+            qc.data = [(self, qargs[:], cargs[:])] * n
+        instruction.definition = qc
         return instruction

qiskit/circuit/library/standard_gates/dcx.py

@@ -54,12 +54,17 @@ def _define(self):
         """
         gate dcx a, b { cx a, b; cx a, b; }
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .x import CXGate
         q = QuantumRegister(2, 'q')
-        self.definition = [
+        qc = QuantumCircuit(q, name=self.name)
+        rules = [
             (CXGate(), [q[0], q[1]], []),
             (CXGate(), [q[1], q[0]], [])
         ]
+        qc.data = rules
+        self.definition = qc
 
     def to_matrix(self):
         """Return a numpy.array for the DCX gate."""

qiskit/circuit/library/standard_gates/h.py

@@ -57,15 +57,16 @@ def _define(self):
         """
         gate h a { u2(0,pi) a; }
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .u2 import U2Gate
-        definition = []
         q = QuantumRegister(1, 'q')
-        rule = [
+        qc = QuantumCircuit(q, name=self.name)
+        rules = [
             (U2Gate(0, pi), [q[0]], [])
         ]
-        for inst in rule:
-            definition.append(inst)
-        self.definition = definition
+        qc.data = rules
+        self.definition = qc
 
     def control(self, num_ctrl_qubits=1, label=None, ctrl_state=None):
         """Return a (multi-)controlled-H gate.
@@ -181,10 +182,12 @@ def _define(self):
             sdg b;
         }
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .x import CXGate  # pylint: disable=cyclic-import
-        definition = []
         q = QuantumRegister(2, 'q')
-        rule = [
+        qc = QuantumCircuit(q, name=self.name)
+        rules = [
             (SGate(), [q[1]], []),
             (HGate(), [q[1]], []),
             (TGate(), [q[1]], []),
@@ -193,9 +196,8 @@ def _define(self):
             (HGate(), [q[1]], []),
             (SdgGate(), [q[1]], [])
         ]
-        for inst in rule:
-            definition.append(inst)
-        self.definition = definition
+        qc.data = rules
+        self.definition = qc
 
     def inverse(self):
         """Return inverted CH gate (itself)."""

qiskit/circuit/library/standard_gates/iswap.py

@@ -92,18 +92,23 @@ def _define(self):
             h q[1];
         }
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .h import HGate
         from .s import SGate
         from .x import CXGate
         q = QuantumRegister(2, 'q')
-        self.definition = [
+        qc = QuantumCircuit(q, name=self.name)
+        rules = [
             (SGate(), [q[0]], []),
             (SGate(), [q[1]], []),
             (HGate(), [q[0]], []),
             (CXGate(), [q[0], q[1]], []),
             (CXGate(), [q[1], q[0]], []),
             (HGate(), [q[1]], [])
         ]
+        qc.data = rules
+        self.definition = qc
 
     def to_matrix(self):
         """Return a numpy.array for the iSWAP gate."""

qiskit/circuit/library/standard_gates/ms.py

@@ -36,14 +36,14 @@ def __init__(self, num_qubits, theta, *, n_qubits=None,  # pylint:disable=unused
         super().__init__('ms', num_qubits, [theta], label=label)
 
     def _define(self):
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .rxx import RXXGate
-        definition = []
         q = QuantumRegister(self.num_qubits, 'q')
-        rule = []
+        qc = QuantumCircuit(q, name=self.name)
+        rules = []
         for i in range(self.num_qubits):
             for j in range(i + 1, self.num_qubits):
-                rule += [(RXXGate(self.params[0]), [q[i], q[j]], [])]
-
-        for inst in rule:
-            definition.append(inst)
-        self.definition = definition
+                rules += [(RXXGate(self.params[0]), [q[i], q[j]], [])]
+        qc.data = rules
+        self.definition = qc

qiskit/circuit/library/standard_gates/r.py

@@ -52,17 +52,18 @@ def _define(self):
         """
         gate r(θ, φ) a {u3(θ, φ - π/2, -φ + π/2) a;}
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .u3 import U3Gate
-        definition = []
         q = QuantumRegister(1, 'q')
+        qc = QuantumCircuit(q, name=self.name)
         theta = self.params[0]
         phi = self.params[1]
-        rule = [
+        rules = [
             (U3Gate(theta, phi - pi / 2, -phi + pi / 2), [q[0]], [])
         ]
-        for inst in rule:
-            definition.append(inst)
-        self.definition = definition
+        qc.data = rules
+        self.definition = qc
 
     def inverse(self):
         """Invert this gate.

qiskit/circuit/library/standard_gates/rx.py

@@ -54,15 +54,16 @@ def _define(self):
         """
         gate rx(theta) a {r(theta, 0) a;}
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .r import RGate
-        definition = []
         q = QuantumRegister(1, 'q')
-        rule = [
+        qc = QuantumCircuit(q, name=self.name)
+        rules = [
             (RGate(self.params[0], 0), [q[0]], [])
         ]
-        for inst in rule:
-            definition.append(inst)
-        self.definition = definition
+        qc.data = rules
+        self.definition = qc
 
     def control(self, num_ctrl_qubits=1, label=None, ctrl_state=None):
         """Return a (mutli-)controlled-RX gate.
@@ -178,21 +179,22 @@ def _define(self):
           u3(theta/2,-pi/2,0) t;
         }
         """
+        # pylint: disable=cyclic-import
+        from qiskit.circuit.quantumcircuit import QuantumCircuit
         from .u1 import U1Gate
         from .u3 import U3Gate
         from .x import CXGate
-        definition = []
         q = QuantumRegister(2, 'q')
-        rule = [
+        qc = QuantumCircuit(q, name=self.name)
+        rules = [
             (U1Gate(pi / 2), [q[1]], []),
             (CXGate(), [q[0], q[1]], []),
             (U3Gate(-self.params[0] / 2, 0, 0), [q[1]], []),
             (CXGate(), [q[0], q[1]], []),
             (U3Gate(self.params[0] / 2, -pi / 2, 0), [q[1]], [])
         ]
-        for inst in rule:
-            definition.append(inst)
-        self.definition = definition
+        qc.data = rules
+        self.definition = qc
 
     def inverse(self):
         """Return inverse RX gate (i.e. with the negative rotation angle)."""