catalyst.adjoint

adjoint(f: Union[Callable, pennylane.operation.Operator], lazy=True) → Union[Callable, pennylane.operation.Operator]

A qjit() compatible adjoint transformer for PennyLane/Catalyst.

Returns a quantum function or operator that applies the adjoint of the provided function or operator.

Warning

This function does not support performing the adjoint of quantum functions that contain mid-circuit measurements.

Parameters

• f (Callable or Operator) – A PennyLane operation or a Python function containing PennyLane quantum operations.

• lazy (bool) – Whether to delay the computation of the Hermitian conjugate until a later time (typically during decomposition or compilation). The default is True, whereas False will immediately produce a new operator implementing the adjoint. Note that False is only supported when the adjoint is applied to a single Operator, rather than a quantum function.

Returns

If an Operator is provided, returns an Operator that is the adjoint. If a function is provided, returns a function with the same call signature that returns the Adjoint of the provided function.

Raises

ValueError – invalid parameter values

Example 1 (basic usage)

@qjit
@qml.qnode(qml.device("lightning.qubit", wires=1))
def workflow(theta, wires):
    catalyst.adjoint(qml.RZ)(theta, wires=wires)
    catalyst.adjoint(qml.RZ(theta, wires=wires))
    def func():
        qml.RX(theta, wires=wires)
        qml.RY(theta, wires=wires)
    catalyst.adjoint(func)()
    return qml.probs()

>>> workflow(jnp.pi/2, wires=0)
Array([0.5, 0.5], dtype=float64)

Example 2 (with Catalyst control flow)

@qjit
@qml.qnode(qml.device("lightning.qubit", wires=1))
def workflow(theta, n, wires):
    def func():
        @catalyst.for_loop(0, n, 1)
        def loop_fn(i):
            qml.RX(theta, wires=wires)

        loop_fn()
    catalyst.adjoint(func)()
    return qml.probs()

>>> workflow(jnp.pi/2, 3, 0)
[1.00000000e+00 7.39557099e-32]

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