AIDT 온디바이스 STEM 공진기 광기계학(Cavity Optomechanics) 복사압 양자 역작용 회피(QBAE) 및 기저상태 냉각 서보 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.Optomechanics
{
    public readonly ref struct OptomechanicalState
    {
        public readonly double DetuningHz;          // 레이저 이조 Delta (Hz)
        public readonly double IntraCavityPhotons;  // 공진기 순환 광자수
        public readonly double MechanicalDisplacementNm; // 기계 진동 변위 (nm)
        public readonly double EffectivePhononCount;// 유효 기계 포논 점유수 n_eff
        public readonly double RadiationForceN;     // 복사압 힘 (N)
        public readonly double SqueezingDb;         // 광 사분면 스퀴징 레벨 (dB)

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public OptomechanicalState(double detuning, double photons, double disp, double nEff, double fRad, double sqz)
        {
            DetuningHz = detuning;
            IntraCavityPhotons = photons;
            MechanicalDisplacementNm = disp;
            EffectivePhononCount = nEff;
            RadiationForceN = fRad;
            SqueezingDb = sqz;
        }
    }

    public ref struct CavityOptomechanicsEngine
    {
        private const double HBar = 1.054571817e-34; // J*s
        private const double C = 299792458.0;        // m/s
        private const double Kb = 1.380649e-23;      // J/K

        private readonly double _omegaM;             // 기계 공진 각주파수 (rad/s)
        private readonly double _gammaM;             // 진동자 고유 감쇠율 (rad/s)
        private readonly double _massKg;             // 유효 진동자 질량 (kg)
        private readonly double _kappa;              // 공진기 선폭 (rad/s)
        private readonly double _g0;                 // 단일 광자 결합 계수 (rad/s)
        private readonly double _bathTempK;          // 열 저장소 온도 (K)

        private double _currentDetuning;             // 현재 이조 주파수 (rad/s)
        private double _laserPowerW;                 // 입력 레이저 전력 (W)
        private double _x;                           // 변위 (m)
        private double _p;                           // 운동량 (kg*m/s)

        public CavityOptomechanicsEngine(double freqMhz, double massNg, double qFactor, double cavityFinesse, double lengthMm, double bathK)
        {
            _omegaM = 2.0 * Math.PI * freqMhz * 1e6;
            _gammaM = _omegaM / qFactor;
            _massKg = massNg * 1e-12;
            _bathTempK = bathK;

            double lengthM = lengthMm * 1e-3;
            double fsr = C / (2.0 * lengthM);
            _kappa = 2.0 * Math.PI * (fsr / cavityFinesse);

            double xZpf = Math.Sqrt(HBar / (2.0 * _massKg * _omegaM));
            double omegaC = 2.0 * Math.PI * (C / 1064e-9); // 1064 nm 레이저
            _g0 = (omegaC / lengthM) * xZpf;

            _currentDetuning = -_omegaM; // 초기 적색 편이
            _laserPowerW = 10e-3;        // 10 mW
            _x = 0.0;
            _p = 0.0;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public OptomechanicalState StepServo(double targetDetuningOffsetHz, double powerModulationW, double dtSec)
        {
            _currentDetuning = -_omegaM + 2.0 * Math.PI * targetDetuningOffsetHz;
            _laserPowerW = Math.Clamp(_laserPowerW + powerModulationW, 1e-4, 0.5);

            // 1. 순환 광자수 및 유효 결합률 계산
            double photonDecay = (_kappa * 0.5) * (_kappa * 0.5) + _currentDetuning * _currentDetuning;
            double intraCavityPhotons = (_kappa * _laserPowerW / (HBar * 2.0 * Math.PI * (C / 1064e-9))) / Math.Max(photonDecay, 1.0);
            double gEff = _g0 * Math.Sqrt(Math.Max(intraCavityPhotons, 0.0));

            // 2. 복사압력 및 광학 감쇠 계산
            double radiationForce = HBar * (_g0 / Math.Sqrt(HBar / (2.0 * _massKg * _omegaM))) * intraCavityPhotons;
            double gammaOpt = (4.0 * gEff * gEff / _kappa) * (1.0 / (1.0 + Math.Pow(2.0 * _currentDetuning / _kappa, 2.0)));

            // 3. 열욕 포논 수 및 동적 유효 포논 점유수 (기저상태 접근율)
            double nThermal = (Kb * _bathTempK) / (HBar * _omegaM);
            double totalGamma = _gammaM + Math.Max(gammaOpt, 0.0);
            double nEff = (_gammaM * nThermal + gammaOpt * 0.1) / Math.Max(totalGamma, 1e-6);

            // 4. 역작용 회피 변조에 따른 양자 폰더로모티브 스퀴징 지표 (dB)
            double cooperativity = (4.0 * gEff * gEff) / (_kappa * _gammaM);
            double squeezingFactor = Math.Max(1.0 + 4.0 * cooperativity / (1.0 + 2.0 * cooperativity), 1.0);
            double squeezingDb = 10.0 * Math.Log10(squeezingFactor);

            // 5. 기계적 변위 동역학 적분 (Euler-Maruyama 근사)
            double acc = (-_massKg * _omegaM * _omegaM * _x - totalGamma * _p / _massKg + radiationForce) / _massKg;
            _p += acc * dtSec;
            _x += (_p / _massKg) * dtSec;

            return new OptomechanicalState(
                detuningHz: _currentDetuning / (2.0 * Math.PI),
                photons: intraCavityPhotons,
                disp: _x * 1e9,
                nEff: nEff,
                fRad: radiationForce,
                sqz: squeezingDb
            );
        }
    }
}