AIDT 온디바이스 STEM 초전도 큐비트 분산 판독(Dispersive Readout) 공진기 서보 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.CircuitQed
{
    public readonly record struct ReadoutParameters(
        double ResonatorOmegaR,    // rad/s (예: 2*pi * 7.0 GHz)
        double DispersiveChi,      // rad/s (예: 2*pi * 2.5 MHz)
        double KappaExt,           // rad/s 외부 커플링 레이트 (예: 2*pi * 5 MHz)
        double KappaInt,           // 내부 손실 레이트
        double ProbeFreqOmegaP     // 프로브 주파수
    );

    public ref struct ReadoutServoState
    {
        public double InPhaseI;
        public double QuadratureQ;
        public double PhaseRad;
        public int ClassifiedState; // 0 or 1
        public double AssignmentFidelity;
        public bool IsDistinguishable;
    }

    public static class DispersiveReadoutServo
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void DemodulateAndClassify(
            in ReadoutParameters p,
            double rawI, double rawQ,
            double integrationWeight,
            ref ReadoutServoState state)
        {
            state.InPhaseI = rawI * integrationWeight;
            state.QuadratureQ = rawQ * integrationWeight;
            state.PhaseRad = Math.Atan2(state.QuadratureQ, state.InPhaseI);

            // 상태 0과 상태 1의 이론적 반사 위상차 계산
            // omega_0 = omega_r - chi, omega_1 = omega_r + chi
            double delta0 = p.ProbeFreqOmegaP - (p.ResonatorOmegaR - p.DispersiveChi);
            double delta1 = p.ProbeFreqOmegaP - (p.ResonatorOmegaR + p.DispersiveChi);

            double totalKappa = p.KappaExt + p.KappaInt;
            double phi0 = Math.Atan2(2.0 * delta0, totalKappa);
            double phi1 = Math.Atan2(2.0 * delta1, totalKappa);

            double midPhaseThreshold = (phi0 + phi1) * 0.5;

            // 판별: 위상 임계값 기준 분류
            if (phi1 > phi0)
            {
                state.ClassifiedState = (state.PhaseRad > midPhaseThreshold) ? 1 : 0;
            }
            else
            {
                state.ClassifiedState = (state.PhaseRad < midPhaseThreshold) ? 1 : 0;
            }

            double sepDist = Math.Abs(phi1 - phi0);
            state.IsDistinguishable = sepDist > 0.2; // 분별 가능 최소 위상차 (약 11도)
            state.AssignmentFidelity = Math.Clamp(1.0 - Math.Exp(-sepDist * 2.5), 0.5, 0.999);
        }
    }
}