AIDT 온디바이스 STEM 미소공진기 폴라리톤 보스-아인슈타인 응축(BEC) 서보 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.QuantumPolaritonics
{
    public readonly record struct PolaritonParameters(
        double ExcitonEnergyEv,   // Ex (예: GaAs 1.52 eV)
        double RabiSplittingMev,  // hbar * Omega_R (예: 10 meV)
        double CavityPhotonMassKg,// m_c ~ 3.0e-36 kg
        double TemperatureK       // 10 K ~ 300 K
    );

    public ref struct PolaritonServoState
    {
        public double DetuningMev;
        public double LowerPolaritonMassKg;
        public double CriticalDensityCm2;
        public double MeasuredK0Intensity;
        public double CoherenceDegree;
        public bool IsCondensateFormed;
    }

    public static class MicrocavityPolaritonServo
    {
        private const double Hbar = 1.054571817e-34; // J*s
        private const double BoltzmannK = 1.380649e-23;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void EvaluateCondensation(
            in PolaritonParameters p,
            double cavityDetuningMev,
            double pumpPowerDensityWcm2,
            double measuredK0Signal,
            ref PolaritonServoState state)
        {
            state.DetuningMev = cavityDetuningMev;
            state.MeasuredK0Intensity = measuredK0Signal;

            // 1. 호프필드(Hopfield) 계수 계산
            // |C|^2 = 0.5 * (1 + delta / sqrt(delta^2 + Omega^2))
            double omegaSq = p.RabiSplittingMev * p.RabiSplittingMev;
            double denom = Math.Sqrt(cavityDetuningMev * cavityDetuningMev + omegaSq);
            double photonFraction = 0.5 * (1.0 - (cavityDetuningMev / denom)); // LP 광자 분율

            // 2. 하부 폴라리톤 유효 질량: m_LP = m_c / |C|^2
            state.LowerPolaritonMassKg = p.CavityPhotonMassKg / Math.Max(0.1, photonFraction);

            // 3. 2차원 BEC 임계 밀도 근사: n_crit = m_pol * k_B * T / (2 * pi * hbar^2) * ln(k_B * T / gamma)
            double prefactor = (state.LowerPolaritonMassKg * BoltzmannK * p.TemperatureK) / (2.0 * Math.PI * Hbar * Hbar);
            double lnTerm = Math.Log(Math.Max(1.1, (BoltzmannK * p.TemperatureK) / (1e-4 * 1.602e-19)));
            double nCritM2 = prefactor * lnTerm;
            state.CriticalDensityCm2 = nCritM2 * 1e-4; // m^-2 -> cm^-2

            // 4. 응축 여부 판정 (펌프 파워가 문턱값 초과 및 k=0 발광 급증)
            double thresholdEst = state.CriticalDensityCm2 * 1e-7; // W/cm^2 근사
            state.IsCondensateFormed = pumpPowerDensityWcm2 > thresholdEst && measuredK0Signal > 5.0;

            // 5. 공간 간섭성 g^(1) 추정 (0.0 ~ 1.0)
            if (state.IsCondensateFormed)
            {
                double overRatio = pumpPowerDensityWcm2 / thresholdEst;
                state.CoherenceDegree = Math.Clamp(1.0 - (0.5 / overRatio), 0.5, 0.98);
            }
            else
            {
                state.CoherenceDegree = 0.05;
            }
        }
    }
}