Adds BasisTanslator, UnrollCustomDefinitions to default levels. (#4446)

* Add Rz->RX,RY, U3->RX,RY, CX->RXX to StandardEquivalenceLibrary.

Updates BasisTranslator-Unroller compatability test
test_basis_translator.TestUnrollerCompatibility.test_unroll_all_instructions
to verify the generated circuit is equivalent (with snapshot,
measure instructions removed) as the circuit transpiled by the
BasisTranslator is no longer gate-for-gate equal with that of the
Unroller.

* Fix free param calculation in standard gates to_matrix test.

Previous code mis-calculated the number of available free parameters
from the gate signature, resulting in creation of gates like
XGate(label=0.1). These would cause errors if the circuits containing
these gates were drawn.

* Remove definition for C3XGate, C4XGate due to name conflict with MCXGate.

* Add UnrollCustomDefinitions and BasisTranslator into default levels.

* Add CX to CZ, to iSwap decompositions.

* Support block collection for non-CX two-qubit gates.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

qiskit/circuit/library/standard_gates/equivalence_library.py

@@ -20,15 +20,14 @@
 from qiskit.qasm import pi
 from qiskit.circuit import EquivalenceLibrary, Parameter, QuantumCircuit, QuantumRegister
 
+from qiskit.quantum_info.synthesis.ion_decompose import cnot_rxx_decompose
+
 from . import (
     HGate,
     CHGate,
     MSGate,
     RGate,
     RCCXGate,
-    RC3XGate,
-    C3XGate,
-    C4XGate,
     RXGate,
     CRXGate,
     RXXGate,
@@ -127,88 +126,6 @@
     def_rccx.append(inst, qargs, cargs)
 _sel.add_equivalence(RCCXGate(), def_rccx)
 
-# RC3XGate
-
-q = QuantumRegister(4, 'q')
-def_rc3x = QuantumCircuit(q)
-for inst, qargs, cargs in [
-        (HGate(), [q[3]], []),
-        (TGate(), [q[3]], []),
-        (CXGate(), [q[2], q[3]], []),
-        (TdgGate(), [q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[0], q[3]], []),
-        (TGate(), [q[3]], []),
-        (CXGate(), [q[1], q[3]], []),
-        (TdgGate(), [q[3]], []),
-        (CXGate(), [q[0], q[3]], []),
-        (TGate(), [q[3]], []),
-        (CXGate(), [q[1], q[3]], []),
-        (TdgGate(), [q[3]], []),
-        (HGate(), [q[3]], []),
-        (TGate(), [q[3]], []),
-        (CXGate(), [q[2], q[3]], []),
-        (TdgGate(), [q[3]], []),
-        (HGate(), [q[3]], []),
-]:
-    def_rc3x.append(inst, qargs, cargs)
-_sel.add_equivalence(RC3XGate(), def_rc3x)
-
-# C3XGate
-
-q = QuantumRegister(4, 'q')
-def_c3x = QuantumCircuit(q)
-for inst, qargs, cargs in [
-        (HGate(), [q[3]], []),
-        (CU1Gate(-pi/4), [q[0], q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[0], q[1]], []),
-        (HGate(), [q[3]], []),
-        (CU1Gate(pi/4), [q[1], q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[0], q[1]], []),
-        (HGate(), [q[3]], []),
-        (CU1Gate(-pi/4), [q[1], q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[1], q[2]], []),
-        (HGate(), [q[3]], []),
-        (CU1Gate(pi/4), [q[2], q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[0], q[2]], []),
-        (HGate(), [q[3]], []),
-        (CU1Gate(-pi/4), [q[2], q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[1], q[2]], []),
-        (HGate(), [q[3]], []),
-        (CU1Gate(pi/4), [q[2], q[3]], []),
-        (HGate(), [q[3]], []),
-        (CXGate(), [q[0], q[2]], []),
-        (HGate(), [q[3]], []),
-        (CU1Gate(-pi/4), [q[2], q[3]], []),
-        (HGate(), [q[3]], [])
-]:
-    def_c3x.append(inst, qargs, cargs)
-_sel.add_equivalence(C3XGate(), def_c3x)
-
-
-# C4XGate
-
-q = QuantumRegister(5, 'q')
-def_c4x = QuantumCircuit(q)
-for inst, qargs, cargs in [
-        (HGate(), [q[4]], []),
-        (CU1Gate(-pi / 2), [q[3], q[4]], []),
-        (HGate(), [q[4]], []),
-        (C3XGate(), [q[0], q[1], q[2], q[3]], []),
-        (HGate(), [q[4]], []),
-        (CU1Gate(pi / 2), [q[3], q[4]], []),
-        (HGate(), [q[4]], []),
-        (C3XGate(), [q[0], q[1], q[2], q[3]], []),
-        (C3XGate(pi / 8), [q[0], q[1], q[2], q[4]], []),
-]:
-    def_c4x.append(inst, qargs, cargs)
-_sel.add_equivalence(C4XGate(), def_c4x)
-
 # RXGate
 
 q = QuantumRegister(1, 'q')
@@ -296,6 +213,14 @@
 def_rz.append(U1Gate(theta), [q[0]], [])
 _sel.add_equivalence(RZGate(theta), def_rz)
 
+q = QuantumRegister(1, 'q')
+theta = Parameter('theta')
+rz_to_rxry = QuantumCircuit(q)
+rz_to_rxry.append(RXGate(pi/2), [q[0]], [])
+rz_to_rxry.append(RYGate(-theta), [q[0]], [])
+rz_to_rxry.append(RXGate(-pi/2), [q[0]], [])
+_sel.add_equivalence(RZGate(theta), rz_to_rxry)
+
 # CRZGate
 
 q = QuantumRegister(2, 'q')
@@ -447,6 +372,18 @@
 
 # U3Gate
 
+q = QuantumRegister(1, 'q')
+theta = Parameter('theta')
+phi = Parameter('phi')
+lam = Parameter('lam')
+u3_qasm_def = QuantumCircuit(q)
+u3_qasm_def.rz(lam, 0)
+u3_qasm_def.rx(pi/2, 0)
+u3_qasm_def.rz(theta+pi, 0)
+u3_qasm_def.rx(pi/2, 0)
+u3_qasm_def.rz(phi+3*pi, 0)
+_sel.add_equivalence(U3Gate(theta, phi, lam), u3_qasm_def)
+
 # CU3Gate
 
 q = QuantumRegister(2, 'q')
@@ -474,6 +411,42 @@
 
 # CXGate
 
+for plus_ry in [False, True]:
+    for plus_rxx in [False, True]:
+        cx_to_rxx = cnot_rxx_decompose(plus_ry, plus_rxx)
+        _sel.add_equivalence(CXGate(), cx_to_rxx)
+
+q = QuantumRegister(2, 'q')
+cx_to_cz = QuantumCircuit(q)
+for inst, qargs, cargs in [
+        (HGate(), [q[1]], []),
+        (CZGate(), [q[0], q[1]], []),
+        (HGate(), [q[1]], [])
+]:
+    cx_to_cz.append(inst, qargs, cargs)
+_sel.add_equivalence(CXGate(), cx_to_cz)
+
+q = QuantumRegister(2, 'q')
+cx_to_iswap = QuantumCircuit(q)
+for inst, qargs, cargs in [
+        (HGate(), [q[0]], []),
+        (XGate(), [q[1]], []),
+        (HGate(), [q[1]], []),
+        (iSwapGate(), [q[0], q[1]], []),
+        (XGate(), [q[0]], []),
+        (XGate(), [q[1]], []),
+        (HGate(), [q[1]], []),
+        (iSwapGate(), [q[0], q[1]], []),
+        (HGate(), [q[0]], []),
+        (SGate(), [q[0]], []),
+        (SGate(), [q[1]], []),
+        (XGate(), [q[1]], []),
+        (HGate(), [q[1]], []),
+]:
+    cx_to_iswap.append(inst, qargs, cargs)
+_sel.add_equivalence(CXGate(), cx_to_iswap)
+
+
 # CCXGate
 
 q = QuantumRegister(3, 'q')

qiskit/compiler/transpile.py

@@ -47,6 +47,7 @@ def transpile(circuits: Union[QuantumCircuit, List[QuantumCircuit]],
               initial_layout: Optional[Union[Layout, Dict, List]] = None,
               layout_method: Optional[str] = None,
               routing_method: Optional[str] = None,
+              translation_method: Optional[str] = None,
               seed_transpiler: Optional[int] = None,
               optimization_level: Optional[int] = None,
               pass_manager: Optional[PassManager] = None,
@@ -119,6 +120,7 @@ def transpile(circuits: Union[QuantumCircuit, List[QuantumCircuit]],
             Sometimes a perfect layout can be available in which case the layout_method
             may not run.
         routing_method: Name of routing pass ('basic', 'lookahead', 'stochastic', 'sabre')
+        translation_method: Name of translation pass ('unroller', 'translator')
         seed_transpiler: Sets random seed for the stochastic parts of the transpiler
         optimization_level: How much optimization to perform on the circuits.
             Higher levels generate more optimized circuits,
@@ -185,7 +187,9 @@ def callback_func(**kwargs):
                                     coupling_map=coupling_map, seed_transpiler=seed_transpiler,
                                     backend_properties=backend_properties,
                                     initial_layout=initial_layout, layout_method=layout_method,
-                                    routing_method=routing_method, backend=backend)
+                                    routing_method=routing_method,
+                                    translation_method=translation_method,
+                                    backend=backend)
 
         warnings.warn("The parameter pass_manager in transpile is being deprecated. "
                       "The preferred way to tranpile a circuit using a custom pass manager is"
@@ -200,7 +204,7 @@ def callback_func(**kwargs):
     # Get transpile_args to configure the circuit transpilation job(s)
     transpile_args = _parse_transpile_args(circuits, backend, basis_gates, coupling_map,
                                            backend_properties, initial_layout,
-                                           layout_method, routing_method,
+                                           layout_method, routing_method, translation_method,
                                            seed_transpiler, optimization_level,
                                            callback, output_name)
 
@@ -274,7 +278,8 @@ def _transpile_circuit(circuit_config_tuple: Tuple[QuantumCircuit, Dict]) -> Qua
     pass_manager_config = transpile_config['pass_manager_config']
 
     ms_basis_swap = None
-    if pass_manager_config.basis_gates is not None:
+    if (pass_manager_config.translation_method == 'unroller'
+            and pass_manager_config.basis_gates is not None):
         # Workaround for ion trap support: If basis gates includes
         # Mølmer-Sørensen (rxx) and the circuit includes gates outside the basis,
         # first unroll to u3, cx, then run MSBasisDecomposer to target basis.
@@ -309,7 +314,7 @@ def _transpile_circuit(circuit_config_tuple: Tuple[QuantumCircuit, Dict]) -> Qua
 
 def _parse_transpile_args(circuits, backend,
                           basis_gates, coupling_map, backend_properties,
-                          initial_layout, layout_method, routing_method,
+                          initial_layout, layout_method, routing_method, translation_method,
                           seed_transpiler, optimization_level,
                           callback, output_name) -> List[Dict]:
     """Resolve the various types of args allowed to the transpile() function through
@@ -336,14 +341,15 @@ def _parse_transpile_args(circuits, backend,
     initial_layout = _parse_initial_layout(initial_layout, circuits)
     layout_method = _parse_layout_method(layout_method, num_circuits)
     routing_method = _parse_routing_method(routing_method, num_circuits)
+    translation_method = _parse_translation_method(translation_method, num_circuits)
     seed_transpiler = _parse_seed_transpiler(seed_transpiler, num_circuits)
     optimization_level = _parse_optimization_level(optimization_level, num_circuits)
     output_name = _parse_output_name(output_name, circuits)
     callback = _parse_callback(callback, num_circuits)
 
     list_transpile_args = []
     for args in zip(basis_gates, coupling_map, backend_properties,
-                    initial_layout, layout_method, routing_method,
+                    initial_layout, layout_method, routing_method, translation_method,
                     seed_transpiler, optimization_level,
                     output_name, callback):
         transpile_args = {'pass_manager_config': PassManagerConfig(basis_gates=args[0],
@@ -352,10 +358,11 @@ def _parse_transpile_args(circuits, backend,
                                                                    initial_layout=args[3],
                                                                    layout_method=args[4],
                                                                    routing_method=args[5],
-                                                                   seed_transpiler=args[6]),
-                          'optimization_level': args[7],
-                          'output_name': args[8],
-                          'callback': args[9]}
+                                                                   translation_method=args[6],
+                                                                   seed_transpiler=args[7]),
+                          'optimization_level': args[8],
+                          'output_name': args[9],
+                          'callback': args[10]}
         list_transpile_args.append(transpile_args)
 
     return list_transpile_args
@@ -446,6 +453,12 @@ def _parse_routing_method(routing_method, num_circuits):
     return routing_method
 
 
+def _parse_translation_method(translation_method, num_circuits):
+    if not isinstance(translation_method, list):
+        translation_method = [translation_method] * num_circuits
+    return translation_method
+
+
 def _parse_seed_transpiler(seed_transpiler, num_circuits):
     if not isinstance(seed_transpiler, list):
         seed_transpiler = [seed_transpiler] * num_circuits

qiskit/quantum_info/synthesis/two_qubit_decompose.py

@@ -36,6 +36,7 @@
 from qiskit.circuit.library.standard_gates.u3 import U3Gate
 from qiskit.circuit.library.standard_gates.x import CXGate
 from qiskit.exceptions import QiskitError
+from qiskit.quantum_info.operators import Operator
 from qiskit.quantum_info.operators.predicates import is_unitary_matrix
 from qiskit.quantum_info.synthesis.weyl import weyl_coordinates
 from qiskit.quantum_info.synthesis.one_qubit_decompose import OneQubitEulerDecomposer
@@ -284,7 +285,8 @@ class TwoQubitBasisDecomposer():
     def __init__(self, gate, basis_fidelity=1.0):
         self.gate = gate
         self.basis_fidelity = basis_fidelity
-        basis = self.basis = TwoQubitWeylDecomposition(gate.to_matrix())
+
+        basis = self.basis = TwoQubitWeylDecomposition(Operator(gate).data)
 
         # FIXME: find good tolerances
         self.is_supercontrolled = np.isclose(basis.a, np.pi/4) and np.isclose(basis.c, 0.)