positioncollapse2d.h

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/**
 * @file positioncollapse2d.h
 * @brief Declares the positioncollapse2d physics/numerical component used by QPE experiments.
 * @ingroup qpe_quantum
 *
 * Source: @c core/quantum/positioncollapse2d.h. This file is part of Quantum Phenomena Explorer (QPE),
 * maintained by Officina Turini. See LICENSE_IT.txt / LICENSE.txt for the
 * QPE freeware source-available terms and THIRD_PARTY_NOTICES.txt for
 * third-party components.
 */
 
#pragma once
 
#include "core/quantum/positionmeasurement2d.h"
 
#include <cstdint>
 
namespace qpe {
 
class ComplexField2D;
 
/**
 * @brief Data record containing Position Collapse2D Result.
 *
 * The structure carries computed data without coupling the numerical component to the GUI or renderer.
 */
struct PositionCollapse2DResult
{
    bool valid = false;
    PositionMeasurement2DPoint outcome;
    double resolution = 0.0;
    double normBefore = 0.0;
    double normAfter = 0.0;
};
 
// Single-system finite-resolution position measurement.
//
// This is deliberately separate from PositionMeasurement2D, which samples an
// ensemble without modifying psi. Here the measurement outcome is drawn from a
// Gaussian-resolution position POVM and the corresponding positive Gaussian
// measurement operator is applied to psi, followed by normalization.
//
// Numerically this avoids the unphysical infinite momentum bandwidth of a
// grid-cell delta collapse while preserving the essential measurement story:
// localization in position broadens momentum space and the collapsed state can
// subsequently evolve again under the same Hamiltonian.
/**
 * @brief Implements the Position Collapse2D component.
 *
 * The class provides one focused service within the QPE architecture and is documented here independently of the experiment-level Help.
 */
class PositionCollapse2D
{
public:
    /**
     * @brief Performs collapse.
     * @param field Field data to read or modify.
     * @param resolution The resolution value used by the operation.
     */
    static PositionCollapse2DResult collapse(ComplexField2D &field,
                                             double resolution);
 
    // Deterministic overload for tests and reproducible demonstrations.
    /**
     * @brief Performs collapse seeded.
     * @param field Field data to read or modify.
     * @param resolution The resolution value used by the operation.
     * @param seed The seed value used by the operation.
     */
    static PositionCollapse2DResult collapseSeeded(ComplexField2D &field,
                                                   double resolution,
                                                   std::uint32_t seed);
};
 
} // namespace qpe