qml.simplify

simplify(input)

Simplifies an operator, tape, qnode or quantum function by reducing its arithmetic depth or number of rotation parameters.

Parameters

input (Operator, MeasurementProcess, pennylane.QNode, QuantumTape, or Callable) – an operator, quantum node, tape or function that applies quantum operations

Returns

(Operator or MeasurementProcess or qnode (QNode) or quantum function (Callable) or tuple[List[QuantumTape], function]): Simplified input. If an operator or measurement process is provided as input, the simplified input is returned directly. Otherwise, the transformed circuit is returned as described in qml.transform.

Example

Given an instantiated operator, qml.simplify reduces the operator’s arithmetic depth:

>>> op = qml.adjoint(qml.RX(0.54, wires=0) + qml.X(0) + qml.Z(1))
>>> op.arithmetic_depth
3
>>> sim_op = qml.simplify(op)
>>> sim_op.arithmetic_depth
2
>>> type(sim_op)
pennylane.ops.op_math.sum.Sum
>>> sim_op.operands
(Adjoint(RX)(0.54, wires=[0]),
Adjoint(PauliX)(wires=[0]),
Adjoint(PauliZ)(wires=[1]))

This function can also simplify the number of rotation gate parameters:

>>> qml.simplify(qml.Rot(np.pi / 2, 0.1, -np.pi / 2, wires=0))
RX(0.1, wires=[0])

Both types of simplification occur together:

>>> op = qml.adjoint(qml.U2(-np.pi/2, np.pi/2, wires=0) + qml.X(0))
>>> op
Adjoint(Sum)([-1.5707963267948966, 1.5707963267948966], [], wires=[0])
>>> qml.simplify(op)
Adjoint(RX)(1.5707963267948966, wires=[0]) + Adjoint(PauliX)(wires=[0])

Moreover, qml.simplify can be used to simplify QNodes or quantum functions:

>>> dev = qml.device("default.qubit", wires=2)
>>> @qml.qnode(dev)
... @qml.simplify
... def circuit():
...     qml.adjoint(qml.prod(qml.RX(1, 0) ** 1, qml.RY(1, 0), qml.RZ(1, 0)))
...     return qml.probs(wires=0)
>>> circuit()
tensor([0.64596329, 0.35403671], requires_grad=True)
>>> list(circuit.tape)
[RZ(11.566370614359172, wires=[0]) @ RY(11.566370614359172, wires=[0]) @ RX(11.566370614359172, wires=[0]),
 probs(wires=[0])]

code/api/pennylane.simplify

 

Download Python script

 

Download Notebook

 

View on GitHub