qrisp.custom_control

custom_control(func)

The custom_control decorator allows to specify the controlled version of the decorated function. If this function is called within a ControlEnvironment or a ConditionEnvironment the controlled version is executed instead.

Specific controlled versions of quantum functions are very common in many scientific publications. This is because the general control procedure can signifcantly increase resource demands.

In order to use the custom_control decorator, you need to add the ctrl keyword to your function signature. If called within a controlled context, this keyword will receive the corresponding control qubit.

For more details consult the examples section.

Parameters

funcfunction

A function of QuantumVariables, which has the ctrl keyword.

Returns

adaptive_control_functionfunction

A function which will execute it’s controlled version, if called within a ControlEnvironment or a ConditionEnvironment.

Examples

We create a swap function with custom control.

from qrisp import mcx, cx, custom_control

@custom_control
def swap(a, b, ctrl = None):

    if ctrl is None:

        cx(a, b)
        cx(b, a)
        cx(a, b)

    else:

        cx(a, b)
        mcx([ctrl, b], a)
        cx(a, b)

Test the non-controlled version:

from qrisp import QuantumBool

a = QuantumBool()
b = QuantumBool()

swap(a, b)

print(a.qs)

QuantumCircuit:
--------------
          ┌───┐     
a.0: ──■──┤ X ├──■──
     ┌─┴─┐└─┬─┘┌─┴─┐
b.0: ┤ X ├──■──┤ X ├
     └───┘     └───┘
Live QuantumVariables:
---------------------
QuantumBool a
QuantumBool b        

Test the controlled version:

from qrisp import control

a = QuantumBool()
b = QuantumBool()
ctrl_qbl = QuantumBool()

with control(ctrl_qbl):

    swap(a,b)

print(a.qs.transpile(1))

                 ┌───┐     
       a.0: ──■──┤ X ├──■──
            ┌─┴─┐└─┬─┘┌─┴─┐
       b.0: ┤ X ├──■──┤ X ├
            └───┘  │  └───┘
ctrl_qbl.0: ───────■───────