[CQT-30] Print out available information instead of "anonymous-gate"

docs/tutorial.md

@@ -152,20 +152,24 @@ except Exception as e:
 
 ## Modifying a circuit
 
-### Merging gates
+### Merging single qubit gates
 
-OpenSquirrel can merge consecutive quantum gates. Currently, this is only done for single-qubit gates. The resulting gate is labeled as an "anonymous gate". Since those gates have no name, the placeholder `<anonymous-gate>` is used instead.
+All single-qubit gates appearing in a circuit can be merged by applying `merge_single_qubit_gates()` to the circuit.
+Note that multi-qubit gates remain untouched and single-qubit gates are not merged across any multi-qubit gates.
+The gate that results from the merger of single-qubit gates will, in general, comprise an arbitrary rotation and, therefore, not be a known gate.
+In OpenSquirrel an unrecognized gate is deemed _anonymous_.
+When a circuit that contains anonymous gates is written to a cQASM string, the semantic representation of the anonymous gate is exported.
+Note that the semantic representation of an anonymous gate is not compliant cQASM.
 
 ```python
 import math
 
-builder = CircuitBuilder(qubit_register_size=1)
-for i in range(16):
-  builder.rx(Qubit(0), Float(math.pi / 16))
+builder = CircuitBuilder(1)
+for i in range(4):
+    builder.Rx(Qubit(0), Float(math.pi / 4))
 
 circuit = builder.to_circuit()
 
-# Merge single qubit gates
 circuit.merge_single_qubit_gates()
 circuit
 ```
@@ -174,15 +178,7 @@ circuit
 
     qubit[1] q
 
-    <anonymous-gate>
-
-You can inspect what the gate has become in terms of the Bloch sphere rotation it represents:
-
-```python
-circuit.ir.statements[0]
-```
-
-    BlochSphereRotation(Qubit[0], axis=[1. 0. 0.], angle=3.141592653589795, phase=0.0)
+    BlochSphereRotation(Qubit[0], axis=[1. 0. 0.], angle=3.14159, phase=0.0)
 
 In the above example, OpenSquirrel has merged all the Rx gates together. Yet, for now, OpenSquirrel does not recognize that this results in a single Rx over the cumulated angle of the individual rotations. Moreover, it does not recognize that the result corresponds to the X-gate (up to a global phase difference). At a later stage, we may want OpenSquirrel to recognize the resultant gate in the case it is part of the set of known gates.
 

opensquirrel/ir.py

@@ -247,6 +247,9 @@ def get_qubit_operands(self) -> list[Qubit]:
 
 
 class Gate(Statement, ABC):
+
+    _significant_digits_repr = 5
+
     def __init__(
         self,
         generator: Callable[..., Gate] | None = None,
@@ -265,7 +268,9 @@ def __eq__(self, other: object) -> bool:
 
     @property
     def name(self) -> str:
-        return self.generator.__name__ if self.generator else "<anonymous-gate>"
+        if self.generator:
+            return self.generator.__name__
+        return self.__repr__()
 
     @property
     def is_anonymous(self) -> bool:
@@ -309,7 +314,10 @@ def identity(q: Qubit) -> BlochSphereRotation:
         return BlochSphereRotation(qubit=q, axis=(1, 0, 0), angle=0, phase=0)
 
     def __repr__(self) -> str:
-        return f"BlochSphereRotation({self.qubit}, axis={self.axis}, angle={self.angle}, phase={self.phase})"
+        axis = np.round(self.axis, self._significant_digits_repr)
+        angle = np.round(self.angle, self._significant_digits_repr)
+        phase = np.round(self.phase, self._significant_digits_repr)
+        return f"BlochSphereRotation({self.qubit}, axis={axis}, angle={angle}, phase={phase})"
 
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, BlochSphereRotation):
@@ -355,7 +363,7 @@ def __init__(
         self.operands = operands
 
     def __repr__(self) -> str:
-        return f"MatrixGate(qubits={self.operands}, matrix={self.matrix})"
+        return f"MatrixGate(qubits={self.operands}, matrix={np.round(self.matrix, self._significant_digits_repr)})"
 
     def accept(self, visitor: IRVisitor) -> Any:
         visitor.visit_gate(self)

test/docs/test_tutorial.py

@@ -0,0 +1,25 @@
+import math
+
+from opensquirrel import CircuitBuilder
+from opensquirrel.ir import Float, Qubit
+
+
+def test_anonymous_gate():
+
+    builder = CircuitBuilder(1)
+    for i in range(4):
+        builder.Rx(Qubit(0), Float(math.pi / 4))
+
+    circuit = builder.to_circuit()
+
+    circuit.merge_single_qubit_gates()
+
+    assert (
+        str(circuit)
+        == """version 3.0
+
+qubit[1] q
+
+BlochSphereRotation(Qubit[0], axis=[1. 0. 0.], angle=3.14159, phase=0.0)
+"""
+    )

test/writer/test_cqasm_lite_writer.py

@@ -51,7 +51,7 @@ def test_anonymous_gate() -> None:
 qubit[2] q
 
 CR(1.234) q[0], q[1]
-<anonymous-gate>
+BlochSphereRotation(Qubit[0], axis=[0.57735 0.57735 0.57735], angle=1.23, phase=0.0)
 CR(1.234) q[0], q[1]
 """
     )

test/writer/test_writer.py

@@ -1,6 +1,9 @@
+import numpy as np
+
+from opensquirrel import CircuitBuilder
 from opensquirrel.circuit import Circuit
 from opensquirrel.default_gates import CR, H
-from opensquirrel.ir import IR, BlochSphereRotation, Comment, Float, Qubit
+from opensquirrel.ir import IR, BlochSphereRotation, Comment, ControlledGate, Float, MatrixGate, Qubit
 from opensquirrel.register_manager import QubitRegister, RegisterManager
 from opensquirrel.writer import writer
 
@@ -36,21 +39,26 @@ def test_write() -> None:
 
 
 def test_anonymous_gate() -> None:
-    register_manager = RegisterManager(QubitRegister(2))
-    ir = IR()
-    ir.add_gate(CR(Qubit(0), Qubit(1), Float(1.234)))
-    ir.add_gate(BlochSphereRotation(Qubit(0), axis=(1, 1, 1), angle=1.23))
-    ir.add_gate(CR(Qubit(0), Qubit(1), Float(1.234)))
-    circuit = Circuit(register_manager, ir)
-
+    qc = CircuitBuilder(2, 2)
+    qc.H(Qubit(0))
+    qc.ir.add_gate(BlochSphereRotation(Qubit(0), axis=(1, 1, 1), angle=1.23))
+    qc.ir.add_gate(ControlledGate(Qubit(0), BlochSphereRotation(Qubit(0), axis=(1, 1, 1), angle=1.23)))
+    qc.ir.add_gate(MatrixGate(np.array([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 0, 1], [0, 0, 1, 0]]), [Qubit(0), Qubit(1)]))
+    qc.CR(Qubit(0), Qubit(1), Float(1.234))
     assert (
-        writer.circuit_to_string(circuit)
+        writer.circuit_to_string(qc.to_circuit())
         == """version 3.0
 
 qubit[2] q
+bit[2] b
 
-CR(1.234) q[0], q[1]
-<anonymous-gate>
+H q[0]
+BlochSphereRotation(Qubit[0], axis=[0.57735 0.57735 0.57735], angle=1.23, phase=0.0)
+ControlledGate(control_qubit=Qubit[0], BlochSphereRotation(Qubit[0], axis=[0.57735 0.57735 0.57735], angle=1.23, phase=0.0))
+MatrixGate(qubits=[Qubit[0], Qubit[1]], matrix=[[1 0 0 0]
+ [0 1 0 0]
+ [0 0 0 1]
+ [0 0 1 0]])
 CR(1.234) q[0], q[1]
 """
     )