from geqo.core.quantum_operation import QuantumOperation
from geqo.core.quantum_circuit import Sequence
from geqo.gates.fundamental_gates import CNOT, Hadamard, Phase
[docs]
class Toffoli(QuantumOperation):
"""Toffoli (CCNOT) gate on three qubits."""
def __init__(self, nameSpacePrefix=""):
"""
The constructor of this class takes a name space prefix, which is used for the internal decomposition of this gate.
Parameters
----------
nameSpacePrefix : String
This string is prepended to all names of internally used gates.
Returns
-------
Toffoli : geqo.gates.multi_qubit_gates.Toffoli
An object of this class that corresponds to the Toffoli gate, i.e. a double-controlled CNOT gate.
"""
self.nameSpacePrefix = nameSpacePrefix
def __repr__(self):
"""
Returns a representation of the object as character string.
-------
string_representation : String
Representation of the object as character string.
"""
return f'Toffoli("{self.nameSpacePrefix}")'
def __eq__(self, other):
"""
Comparator with other objects.
Parameters
----------
other : An object, which should be compared to this object.
Returns
-------
True : If the provided object is of the same type and if the name space prefixes are the same.
False : else
"""
if not isinstance(other, Toffoli):
return False
else:
return self.nameSpacePrefix == other.nameSpacePrefix
[docs]
def getInverse(self):
"""
Return the same object, because it is inverse to itself.
Returns
-------
Toffoli : geqo.gates.multi_qubit_gates.Toffoli
Return the object, because it is self-inverse.
"""
return self
[docs]
def getEquivalentSequence(self):
"""
Return an object of the class ```Sequence```, which contains several operations that correspond to
the Toffoli gate. The name space prefix is prepended to all internal gates when needed.
Returns
-------
sequence : geqo.core.Sequence
An object of the class ```Sequence``` without operations, but with the appropriate bits and qubits.
The name space prefix is prepended to all internal gates when needed.
"""
phPlusPi = Phase(self.nameSpacePrefix + "S.Pi/4")
phMinusPi = Phase(self.nameSpacePrefix + "-S.Pi/4")
seq = [
(Hadamard(), [2]),
(CNOT(), [1, 2]),
(phMinusPi, [2]),
(CNOT(), [0, 2]),
(phPlusPi, [2]),
(CNOT(), [1, 2]),
(phMinusPi, [2]),
(CNOT(), [0, 2]),
(phPlusPi, [1]),
(phPlusPi, [2]),
(CNOT(), [0, 1]),
(Hadamard(), [2]),
(phPlusPi, [0]),
(phMinusPi, [1]),
(CNOT(), [0, 1]),
]
return Sequence([], [0, 1, 2], seq)
[docs]
def getNumberQubits(self):
"""
Return the number of qubits that are used by this permuation operation.
Returns
-------
3 : int
The Toffoli gate acts on 3 qubits.
"""
return 3
[docs]
def getNumberClassicalBits(self):
"""
Returns
-------
0 : int
The number of classical bits, which are used by PermuteQubits, is zero.
"""
return 0
[docs]
def hasDecomposition(self):
"""
Returns
-------
True : Bool
The Toffoli gate can be decomposed into a sequence of simpler gates.
"""
return True
[docs]
def isUnitary(self):
"""
Returns
-------
True : Bool
This is a unitary operation.
"""
return True
