import numpy as np


def _apply_quantum_enhancement(self, data: np.ndarray) -> np.ndarray:
    """Apply quantum enhancement to the input data."""
    if not self.initialized or self.quantum_state is None:
        raise RuntimeError("QuantumEnhancer must be initialized before use")

    # Normalize input data
    normalized_data = self._normalize_data(data)

    # Apply quantum operations
    quantum_state = self._prepare_quantum_state(normalized_data)
    quantum_state = self._apply_enhancement_gates(quantum_state)

    # Measure and process results
    measurements = self._measure_quantum_state(quantum_state)
    return self._process_measurements(measurements)
