Source code for qplex.algorithms.mixers.cardinality_mixer

from typing import List

from qplex.algorithms.mixers.quantum_mixer import QuantumMixer




class CardinalityMixer(QuantumMixer):
    """XY-mixer implementation for problems with cardinality constraints.

    Implements an XY-mixing Hamiltonian that preserves the Hamming weight of the
    quantum state, suitable for problems with fixed-sum or cardinality constraints.
    """



    def generate_circuit(self, n_qubits: int, theta: str) -> List[str]:
        """Generate circuit for XY-mixing operation.

        Creates a series of controlled operations between qubit pairs to implement
        the XY-mixer while preserving total number of 1s in the state.

        Parameters
        ----------
        n_qubits : int
            Number of qubits
        theta : str
            Mixing angle parameter

        Returns
        -------
        List[str]
            OpenQASM3 instructions for XY-mixer
        """
        lines = []
        for i in range(n_qubits):
            for j in range(i + 1, n_qubits):
                lines.extend([
                    f"h q[{i}];", f"h q[{j}];",
                    f"cx q[{i}], q[{j}];",
                    f"rz({theta}) q[{j}];",
                    f"cx q[{i}], q[{j}];",
                    f"h q[{i}];", f"h q[{j}];"
                ])
        return lines