[CQT-485] Try to replace generic TwoQubitGate with gate from default two-qubit gate set

opensquirrel/default_instructions.py

@@ -86,6 +86,11 @@
     **default_bsr_with_param_set,
 }
 
+default_two_qubit_gate_with_param_set: dict[str, type[TwoQubitGate]] = {
+    "CRk": CRk,
+    "CR": CR,
+}
+
 default_two_qubit_gate_set: dict[str, type[TwoQubitGate]] = {
     "CNOT": CNOT,
     "CR": CR,
@@ -116,6 +121,7 @@
     "Identity": I,
     "Toffoli": CCX,
 }
+
 default_gate_set: dict[str, type[Gate]] = {
     **default_single_qubit_gate_set,
     **default_two_qubit_gate_set,
@@ -128,10 +134,12 @@
     "measure": Measure,
     "reset": Reset,
 }
+
 default_control_instruction_set: dict[str, type[ControlInstruction]] = {
     "barrier": Barrier,
     "wait": Wait,
 }
+
 default_instruction_set: dict[str, type[Instruction]] = {
     **default_gate_set,
     **default_non_unitary_set,

opensquirrel/ir/two_qubit_gate.py

@@ -1,12 +1,60 @@
+from __future__ import annotations
+
 from functools import cached_property
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 import numpy as np
 
 from opensquirrel.ir import Gate, IRVisitor, Qubit, QubitLike
-from opensquirrel.ir.semantics import CanonicalGateSemantic, ControlledGateSemantic, MatrixGateSemantic
+from opensquirrel.ir.semantics import (
+    CanonicalGateSemantic,
+    ControlledGateSemantic,
+    MatrixGateSemantic,
+)
 from opensquirrel.ir.semantics.bsr import bsr_from_matrix
-from opensquirrel.ir.semantics.gate_semantic import GateSemantic
+
+if TYPE_CHECKING:
+    from opensquirrel.ir.semantics.gate_semantic import GateSemantic
+
+
+def try_match_replace_with_default_two_qubit_gate(gate: TwoQubitGate) -> TwoQubitGate:
+    """Tries to match a given two-qubit gate with a _default_ two-qubit gate.
+    It does that by checking if the two-qubit gates matches one of the _default_ two-qubit gates.
+
+    Note:
+        - The default (two-qubit) gates are defined in the
+        [cQASM standard gate set](https://qutech-delft.github.io/cQASM-spec/latest/standard_gate_set/index.html).
+        - If no specific match is found, the input gate is returned unmodified.
+        - The parameterized two-qubit gates (e.g., CR, CRk) are not included in the default two-qubit gate set.
+
+    Args:
+        gate: The two-qubit gate to be matched.
+
+    Returns:
+        A default two-qubit gate if this two-qubit gate matches it, otherwise return the input gate.
+
+    """
+    from opensquirrel.default_instructions import (
+        default_two_qubit_gate_set,
+        default_two_qubit_gate_with_param_set,
+    )
+
+    if gate.name in default_two_qubit_gate_set:
+        return gate
+
+    default_gates = {
+        gate_name: gate_type
+        for gate_name, gate_type in default_two_qubit_gate_set.items()
+        if gate_name not in default_two_qubit_gate_with_param_set
+    }
+
+    for gate_type in default_gates.values():
+        arguments: tuple[Any, ...] = (gate.qubit0, gate.qubit1)
+        possible_gate = gate_type(*arguments)  # ty: ignore[missing-argument]
+        if possible_gate == gate:
+            return possible_gate
+
+    return gate
 
 
 class TwoQubitGate(Gate):

opensquirrel/writer/writer.py

@@ -29,7 +29,7 @@
 )
 from opensquirrel.ir.single_qubit_gate import SingleQubitGate, try_match_replace_with_default_gate
 from opensquirrel.ir.three_qubit_gate import ThreeQubitGate
-from opensquirrel.ir.two_qubit_gate import TwoQubitGate
+from opensquirrel.ir.two_qubit_gate import TwoQubitGate, try_match_replace_with_default_two_qubit_gate
 from opensquirrel.register_manager import RegisterManager
 
 
@@ -88,6 +88,7 @@ def visit_single_qubit_gate(self, gate: SingleQubitGate) -> None:
         self.output += f"{gate.name}{bsr_parameters} {qubit_operand}\n"
 
     def visit_two_qubit_gate(self, gate: TwoQubitGate) -> Any:
+        gate = try_match_replace_with_default_two_qubit_gate(gate)
         qubit_operand_0 = gate.qubit0.accept(self)
         qubit_operand_1 = gate.qubit1.accept(self)
 

tests/ir/test_two_qubit_gate.py

@@ -2,13 +2,52 @@
 import pytest
 from numpy.typing import NDArray
 
-from opensquirrel import CNOT, CV, DCNOT, ISWAP, SWAP, InvSqrtSWAP, SqrtISWAP, SqrtSWAP
+from opensquirrel import CNOT, CV, CY, CZ, DCNOT, ECR, ISWAP, MS, SWAP, InvSqrtSWAP, M, SqrtISWAP, SqrtSWAP
 from opensquirrel.ir import Qubit
 from opensquirrel.ir.semantics import BlochSphereRotation, CanonicalGateSemantic, MatrixGateSemantic
-from opensquirrel.ir.two_qubit_gate import TwoQubitGate
+from opensquirrel.ir.two_qubit_gate import TwoQubitGate, try_match_replace_with_default_two_qubit_gate
 from opensquirrel.utils.matrix_expander import can2, get_matrix
 
 
+@pytest.mark.parametrize(
+    ("gate", "default_gate"),
+    [
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(CNOT(1, 0), 2))), CNOT(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(CV(1, 0), 2))), CV(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(CY(1, 0), 2))), CY(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(CZ(1, 0), 2))), CZ(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(DCNOT(1, 0), 2))), DCNOT(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(ECR(1, 0), 2))), ECR(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(InvSqrtSWAP(1, 0), 2))), InvSqrtSWAP(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(ISWAP(1, 0), 2))), ISWAP(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(M(1, 0), 2))), M(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(MS(1, 0), 2))), MS(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(SqrtISWAP(1, 0), 2))), SqrtISWAP(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(SqrtSWAP(1, 0), 2))), SqrtSWAP(0, 1)),
+        (TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic(get_matrix(SWAP(1, 0), 2))), SWAP(0, 1)),
+    ],
+    ids=[
+        "CNOT",
+        "CV",
+        "CY",
+        "CZ",
+        "DCNOT",
+        "ECR",
+        "InvSqrtSWAP",
+        "ISWAP",
+        "M",
+        "MS",
+        "SqrtISWAP",
+        "SqrtSWAP",
+        "SWAP",
+    ],
+)
+def test_default_gate_matching(gate: TwoQubitGate, default_gate: TwoQubitGate) -> None:
+    matched_gate = try_match_replace_with_default_two_qubit_gate(gate)
+    assert matched_gate == default_gate
+    assert matched_gate.name == default_gate.name
+
+
 class TestTwoQubitGate:
     @pytest.fixture
     def gate(self) -> TwoQubitGate:

tests/writer/test_writer.py

@@ -2,7 +2,7 @@
 
 from opensquirrel import CircuitBuilder
 from opensquirrel.ir.expression import Axis
-from opensquirrel.ir.semantics import BlochSphereRotation, ControlledGateSemantic, MatrixGateSemantic
+from opensquirrel.ir.semantics import BlochSphereRotation, ControlledGateSemantic
 from opensquirrel.ir.single_qubit_gate import SingleQubitGate
 from opensquirrel.ir.two_qubit_gate import TwoQubitGate
 from opensquirrel.writer import writer
@@ -213,9 +213,7 @@ def test_anonymous_gate() -> None:
             gate_semantic=ControlledGateSemantic(target_bsr=BlochSphereRotation(axis=(1, 1, 1), angle=1.23, phase=0.0)),
         )
     )
-    builder.ir.add_gate(
-        TwoQubitGate(0, 1, gate_semantic=MatrixGateSemantic([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 0, 1], [0, 0, 1, 0]]))
-    )
+
     builder.CR(0, 1, 1.234)
     assert (
         str(builder.to_circuit())
@@ -227,7 +225,6 @@ def test_anonymous_gate() -> None:
 H q[0]
 Rn(0.57735027, 0.57735027, 0.57735027, 1.23, 0.0) q[0]
 TwoQubitGate(qubits=[(Qubit[0], Qubit[1])], gate_semantic=ControlledGateSemantic(target_bsr=BlochSphereRotation(axis=[0.57735 0.57735 0.57735], angle=1.23, phase=0.0)))
-TwoQubitGate(qubits=[(Qubit[0], Qubit[1])], gate_semantic=MatrixGateSemantic(matrix=[[1.+0.j 0.+0.j 0.+0.j 0.+0.j] [0.+0.j 1.+0.j 0.+0.j 0.+0.j] [0.+0.j 0.+0.j 0.+0.j 1.+0.j] [0.+0.j 0.+0.j 1.+0.j 0.+0.j]]))
 CR(1.234) q[0], q[1]
 """  # ruff: ignore[line-too-long]
     )