feature: added controlled-sqrt-not gate (#297)

* feature: added controlled-sqrt-not gate This makes certain circuits, like CHSH, more straightforward. This commit works in line with the following branches (also committed, separately): https://github.com/unprovable/amazon-braket-schemas-python.git@ctrl-v-gate https://github.com/unprovable/amazon-braket-default-simulator-python.git@ctrl-v-gate * fix: ran tox linters * fix: reverted tox.ini Co-authored-by: Mark C <[email protected]> Co-authored-by: Mark C <[email protected]> Co-authored-by: Cody Wang <[email protected]>
amazon-braket · Jan 27, 2022 · f316017 · f316017
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commit f316017
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diff --git a/src/braket/circuits/gates.py b/src/braket/circuits/gates.py
@@ -1237,6 +1237,51 @@ def cphaseshift10(
 Gate.register_gate(CPhaseShift10)
 
 
+class CV(Gate):
+    """Controlled Sqrt of NOT gate."""
+
+    def __init__(self):
+        super().__init__(qubit_count=None, ascii_symbols=["C", "V"])
+
+    def to_ir(self, target: QubitSet):
+        return ir.CV.construct(control=target[0], target=target[1])
+
+    def to_matrix(self) -> np.ndarray:
+        return np.array(
+            [
+                [1.0, 0.0, 0.0, 0.0],
+                [0.0, 1.0, 0.0, 0.0],
+                [0.0, 0.0, 0.5 + 0.5j, 0.5 - 0.5j],  # if the control bit, then apply the V gate
+                [0.0, 0.0, 0.5 - 0.5j, 0.5 + 0.5j],  # which is the sqrt(NOT) gate.
+            ],
+            dtype=complex,
+        )
+
+    @staticmethod
+    def fixed_qubit_count() -> int:
+        return 2
+
+    @staticmethod
+    @circuit.subroutine(register=True)
+    def cv(control: QubitInput, target: QubitInput) -> Instruction:
+        """Registers this function into the circuit class.
+
+        Args:
+            control (Qubit or int): Control qubit index.
+            target (Qubit or int): Target qubit index.
+
+        Returns:
+            Instruction: CV instruction.
+
+        Examples:
+            >>> circ = Circuit().cv(0, 1)
+        """
+        return Instruction(CV(), target=[control, target])
+
+
+Gate.register_gate(CV)
+
+
 class CY(Gate):
     """Controlled Pauli-Y gate."""
 

diff --git a/test/unit_tests/braket/circuits/test_gates.py b/test/unit_tests/braket/circuits/test_gates.py
@@ -42,6 +42,7 @@
     (Gate.Ry, "ry", ir.Ry, [SingleTarget, Angle], {}),
     (Gate.Rz, "rz", ir.Rz, [SingleTarget, Angle], {}),
     (Gate.CNot, "cnot", ir.CNot, [SingleTarget, SingleControl], {}),
+    (Gate.CV, "cv", ir.CV, [SingleTarget, SingleControl], {}),
     (Gate.CCNot, "ccnot", ir.CCNot, [SingleTarget, DoubleControl], {}),
     (Gate.Swap, "swap", ir.Swap, [DoubleTarget], {}),
     (Gate.CSwap, "cswap", ir.CSwap, [SingleControl, DoubleTarget], {}),

diff --git a/tox.ini b/tox.ini
@@ -89,4 +89,4 @@ commands =
 deps =
     # If you need to test on a certain branch, add @<branch-name> after .git
     git+https://github.com/aws/amazon-braket-schemas-python.git
-    git+https://github.com/aws/amazon-braket-default-simulator-python.git
+    git+https://github.com/aws/amazon-braket-default-simulator-python.git