feature: Added counts based on operator name and qubits specified

src/braket/circuits/circuit.py

@@ -1626,6 +1626,71 @@ def _add_fixed_argument_calibrations(
                 })
         return additional_calibrations
 
+    def count(
+        self,
+        operator: str | None = None,
+        qubits: QubitSet | None = None,
+        include_noise: bool = False,
+    ) -> int | Counter[str]:
+        """Counts circuit instructions by operator name, optionally filtered by specific
+        operators and/or qubits.
+
+        Args:
+            operator (str | None): Optional operator name to count. Matching is case-insensitive.
+                If not provided, returns counts for all operator names.
+            qubits (QubitSet | None): Optional set of qubits to consider. If not provided,
+                considers all qubits.
+            include_noise (bool): Whether to include noise instructions in the count.
+                Default is False.
+
+        Returns:
+            int | Counter[str]: The count for ``operator`` if provided, otherwise a ``Counter``
+            keyed by operator name.
+
+        Raises:
+            ValueError: If any qubits in ``qubits`` are not present in the circuit
+
+        Examples:
+            >>> circuit = Circuit().h(0).h(1).cnot(0, 1).amplitude_damping(0, gamma=0.1)
+            >>> circuit.count("cnot")
+            1
+            >>> circuit.count()
+            Counter({'cnot': 1, 'h': 2})
+            >>> circuit.count(qubits={0})
+            Counter({'cnot': 1, 'h': 1})
+            >>> circuit.count(qubits={0}, operator="h")
+            1
+            >>> circuit.count(include_noise=True)
+            Counter({'cnot': 1, 'h': 2, 'amplitudedamping': 1})
+        """
+        counts: dict[str, int] = {}
+
+        # to avoid erroring on qubits that are part of the circuit but not targeted
+        # by any instruction we construct the following set as opposed to just using
+        # :attr:`self.qubits` directly
+        circuit_qubits = set(
+            set(range(min(self.qubits), max(self.qubits) + 1)) if self.qubits else set()
+        )
+
+        if qubits and qubits.intersection(circuit_qubits) != qubits:
+            raise ValueError(
+                "All qubits in the 'qubits' argument must be present in the circuit. "
+                f"Invalid qubits: {qubits - circuit_qubits}"
+            )
+
+        for instruction in self.instructions:
+            if qubits and not set(instruction.target).intersection(qubits):
+                continue
+            if not include_noise and isinstance(instruction.operator, Noise):
+                continue
+            name = instruction.operator.name.lower()
+            counts[name] = counts.get(name, 0) + 1
+
+        if operator:
+            return counts.get(operator.lower(), 0)
+
+        return Counter(counts)
+
     def to_unitary(self) -> np.ndarray:
         """Returns the unitary matrix representation of the entire circuit.
 

test/unit_tests/braket/circuits/test_circuit.py

@@ -3831,3 +3831,30 @@ def test_barrier_jaqcd_export_fails():
         pytest.raises(NotImplementedError, match="Barrier is not supported in JAQCD"),
     ):
         circ.to_ir(IRType.JAQCD)
+
+
+def test_circuit_count_ops():
+    circ = Circuit().h(0).h(1).cnot(0, 1).measure([0, 1]).gphase(0.5)
+    assert circ.count("cnot") == 1
+    assert circ.count("h") == 2
+    assert circ.count("unknown") == 0
+    assert circ.count() == {"cnot": 1, "h": 2, "measure": 2, "gphase": 1}
+    assert circ.count(qubits={0, 1}) == {"cnot": 1, "h": 2, "measure": 2}
+    assert circ.count(qubits={0}) == {"cnot": 1, "h": 1, "measure": 1}
+    assert circ.count(qubits={0}, operator="h") == 1
+
+    circ = Circuit().cnot(0, 2)
+    assert circ.count(qubits={1}) == {}
+
+    circ = Circuit().amplitude_damping(0, gamma=0.1)
+
+    assert circ.count() == {}
+    assert circ.count(include_noise=True) == {"amplitudedamping": 1}
+    assert circ.count(qubits={0}, include_noise=True) == {"amplitudedamping": 1}
+    assert circ.count(operator="amplitudedamping", include_noise=True) == 1
+
+    with pytest.raises(
+        ValueError,
+        match="All qubits in the 'qubits' argument must be present in the circuit",
+    ):
+        circ.count(qubits={3})