다이아몬드 NV 센터 램지 간섭계 양자 결맞음 & 1,000Hz 0-Alloc C# 피코테슬라 신경 자기장 계측 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.QuantumBioMagnetometry
{
    /// <summary>
    /// 다이아몬드 NV 광학 형광 및 램지 간섭 계측 상태 구조체
    /// </summary>
    public readonly ref struct NvRamseyState
    {
        public double FreePrecessionTimeNs { get; }  // 세차 시간 tau (ns)
        public double FluorescenceCountPhoton { get; }// 광자 카운트 (counts)
        public double MicrowaveFreqOffsetMhz { get; }// RF 디튜닝 (MHz)
        public double ContrastPercent { get; }       // 신호 대비도 C (%)
        public double AmbientFieldMicroT { get; }    // 배경 바이어스 자기장 (uT)

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public NvRamseyState(double tau, double counts, double offset, double contrast, double bias)
        {
            FreePrecessionTimeNs = tau;
            FluorescenceCountPhoton = counts;
            MicrowaveFreqOffsetMhz = offset;
            ContrastPercent = contrast;
            AmbientFieldMicroT = bias;
        }
    }

    /// <summary>
    /// 1,000Hz 0-Alloc C# 램지 프린지 복조 및 피코테슬라 신경 신호 복원 엔진
    /// </summary>
    public ref struct NvNeuralMagnetometryEngine
    {
        // NV 전자 자기회전비 gamma_e / (2*pi) = 28.024 GHz/T = 28.024 Hz/nT
        public const double GyromagneticRatioHzPerTesla = 2.802495164e10;

        private double _baselineFluorescence;
        private double _accumulatedMagneticFieldPt;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public NvNeuralMagnetometryEngine(double baselineCounts)
        {
            _baselineFluorescence = baselineCounts;
            _accumulatedMagneticFieldPt = 0.0;
        }

        /// <summary>
        /// 1,000Hz 실시간 루프 (dt = 0.001s) 위상 역산 및 활동전위 자기장 검출
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void ProcessStep(
            in NvRamseyState state,
            out double neuralFieldPicoTesla,
            out double phaseShiftRad,
            out bool isActionPotentialSpike,
            out double snrMetricDb)
        {
            // 1. 정규화된 형광 비율 S / S0
            double normSignal = state.FluorescenceCountPhoton / Math.Max(1.0, _baselineFluorescence);
            double contrastFactor = state.ContrastPercent * 0.01;

            // 2. 램지 프린지 선형 동작점(Half-Maximum) 역위상 산출
            // S = S0 * [1 - C/2 + C * delta_phi] -> delta_phi ~ (normSignal - (1 - C/2)) / C
            double midpoint = 1.0 - (0.5 * contrastFactor);
            double deltaPhase = (normSignal - midpoint) / Math.Max(0.001, contrastFactor);
            phaseShiftRad = Math.Clamp(deltaPhase, -Math.PI / 2.0, Math.PI / 2.0);

            // 3. 자기장 역산: B = delta_phi / (gamma_e * tau)
            double tauSec = state.FreePrecessionTimeNs * 1e-9;
            double estimatedFieldTesla = phaseShiftRad / (GyromagneticRatioHzPerTesla * tauSec);
            neuralFieldPicoTesla = estimatedFieldTesla * 1e12; // pT 변환

            // 4. 신경 세포 활동전위 스파이크 판정 (임계값: 15 pT 이상)
            isActionPotentialSpike = Math.Abs(neuralFieldPicoTesla) >= 15.0;

            // 5. 샷 노이즈 대비 SNR 계산
            double shotNoise = 1.0 / Math.Sqrt(Math.Max(1.0, state.FluorescenceCountPhoton));
            snrMetricDb = 20.0 * Math.Log10(Math.Max(1e-4, Math.Abs(phaseShiftRad) / shotNoise));

            _accumulatedMagneticFieldPt = neuralFieldPicoTesla;
        }
    }
}