quantum_state.hpp

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#pragma once
 
/**
 * QuantumState — generic quantum state.
 *
 * A single quantum state consisting of a wavefunction,
 * its energy eigenvalue, and its occupation number.
 * Templated on the wavefunction type, which is
 * representation-specific (defined in layer 3).
 */
 
#include "layer_0_core/types/init.hpp"
 
namespace q3 {
 
/**
 * A single quantum state: wavefunction + eigenvalue + occupation.
 */
template <typename WavefunctionType> struct QuantumState {
    /// The wavefunction (representation-specific).
    WavefunctionType wavefunction;
 
    /// Energy eigenvalue in Rydberg.
    Real eigenvalue = 0.0;
 
    /// Occupation number (0.0 to 1.0 per spin channel).
    Real occupation = 0.0;
 
    /// Whether this state is occupied.
    [[nodiscard]] bool is_occupied() const {
        return occupation > 0.0;
    }
};
 
} // namespace q3