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Comparator

QuICT.algorithm.arithmetic.basic.Comparator 

Comparator(qreg_size: int, const: int, in_fourier: bool = False, out_fourier: bool = False, mode: str = 'lt', name: str = None)

Bases: CompositeGate

In "lt" (less than) mode: U(c)|x>|0> --> |x>|x < c> In "ge" (greater than or equal) mode: U(c)|x>|0> --> |x>|x >= c>

Parameters:

  • qreg_size (int) –

    Size of the quantum register.

  • const (int) –

    The integer to be compared with, given classically.

  • name (str, default: None ) –

    Name of the gate.

Source code in QuICT/algorithm/arithmetic/basic/comparator.py 
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def __init__(
    self,
    qreg_size: int,
    const: int,
    in_fourier: bool = False,
    out_fourier: bool = False,
    mode: str = "lt",
    name: str = None
):
    """
    Args:
        qreg_size (int): Size of the quantum register.
        const (int): The integer to be compared with, given classically.
        name (str): Name of the gate.
    """
    if mode not in ["lt", "ge"]:
        raise ValueError("Not a valid mode, pealse choose from: \"lt\", \"ge\"}.")
    # TODO: check `qreg_size` can hold `const` as a signed int
    super().__init__(name)

    self._data_reg = list(range(qreg_size))
    self._sign_reg = [qreg_size]

    QFTWiredAdder(qreg_size, -const, in_fourier=in_fourier) | self(self._data_reg)
    if mode == "ge":
        X | self(self._data_reg[0])
    CX | self([self._data_reg[0], self._sign_reg[0]])
    if mode == "ge":
        X | self(self._data_reg[0])
    QFTWiredAdder(qreg_size, const, out_fourier=out_fourier) | self(self._data_reg)