조셉슨 파라메트릭 증폭기(JPA) 양자 압축 & 1,000Hz 0-Alloc C# 큐비트 판독 펌프 위상 잠금 서보 제어기

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace ZeliDesk.Defense.QuantumPhysics
{
    /// <summary>
    /// JPA I/Q 복조 신호 및 마이크로파 텔레메트리 프레임
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct JpaTelemetryFrame
    {
        public readonly double TimestampSeconds;
        public readonly double InPhaseMean;           // In-phase 신호 평균 (V)
        public readonly double QuadratureMean;        // Quadrature 신호 평균 (V)
        public readonly double VarianceI;             // I 채널 잡음 분산 (V^2)
        public readonly double VarianceQ;             // Q 채널 잡음 분산 (V^2)
        public readonly double SQUID_FluxBiasCurrentA;// 현재 자속 바이어스 전류 (A)

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public JpaTelemetryFrame(double timestamp, double iMean, double qMean, double varI, double varQ, double fluxCurrent)
        {
            TimestampSeconds = timestamp;
            InPhaseMean = iMean;
            QuadratureMean = qMean;
            VarianceI = varI;
            VarianceQ = varQ;
            SQUID_FluxBiasCurrentA = fluxCurrent;
        }
    }

    /// <summary>
    /// JPA 펌프 위상 및 자속 바이어스 제어 출력 프레임
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct JpaControlOutput
    {
        public readonly double CommandedPumpPhaseDegrees; // 지령 펌프 위상각 (deg)
        public readonly double CommandedFluxCurrentA;     // 지령 자속 코일 전류 (A)
        public readonly double SqueezingDecibels;         // 측정된 양자 압축도 (dB)
        public readonly double ReadoutFidelityEstimate;   // 추정 큐비트 판독 충실도 (0.0 ~ 1.0)
        public readonly bool IsPumpPhaseLocked;           // 위상 록인 사수 플래그

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public JpaControlOutput(double phaseDeg, double fluxCur, double sqDb, double fidelity, bool isLocked)
        {
            CommandedPumpPhaseDegrees = phaseDeg;
            CommandedFluxCurrentA = fluxCur;
            SqueezingDecibels = sqDb;
            ReadoutFidelityEstimate = fidelity;
            IsPumpPhaseLocked = isLocked;
        }
    }

    /// <summary>
    /// 1,000Hz 0-Alloc C# 조셉슨 파라메트릭 증폭기 위상 잠금 서보 엔진
    /// </summary>
    public ref struct JpaPumpPhaseServoEngine
    {
        private const double TargetPhaseDeg = 45.0;      // 최적 직교 압축 타겟 위상각 (deg)
        private const double VacuumNoiseVariance = 1e-4; // 표준 양자 진공 잡음 분산 (V^2)

        // PI 제어 게인
        private const double Kp = 1.6;
        private const double Ki = 0.25;

        private double _accumulatedPhaseError;
        private double _currentPumpPhase;
        private double _currentFluxCurrent;
        private double _lastTimestamp;
        private bool _isInitialized;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Initialize(double initialPhaseDeg, double initialFluxA)
        {
            _accumulatedPhaseError = 0.0;
            _currentPumpPhase = initialPhaseDeg;
            _currentFluxCurrent = initialFluxA;
            _lastTimestamp = 0.0;
            _isInitialized = true;
        }

        /// <summary>
        /// 1,000Hz(1ms 주기) I/Q 텔레메트리 기반 펌프 위상 및 자속 보정 틱
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public JpaControlOutput ProcessTick(in JpaTelemetryFrame frame)
        {
            if (!_isInitialized)
            {
                Initialize(45.0, frame.SQUID_FluxBiasCurrentA);
            }

            double dt = frame.TimestampSeconds - _lastTimestamp;
            if (dt <= 0.0 || dt > 0.01) dt = 0.001; // 1ms 기본 주기
            _lastTimestamp = frame.TimestampSeconds;

            // 1. 순간 I/Q 위상각 산출: theta = atan2(Q, I)
            double measuredPhaseRad = Math.Atan2(frame.QuadratureMean, frame.InPhaseMean);
            double measuredPhaseDeg = measuredPhaseRad * (180.0 / Math.PI);

            // 2. 양자 잡음 압축도(Squeezing, dB) 산출
            double minVariance = Math.Min(frame.VarianceI, frame.VarianceQ);
            double squeezingDb = 0.0;
            if (minVariance > 0.0)
            {
                squeezingDb = -10.0 * Math.Log10(minVariance / VacuumNoiseVariance);
                squeezingDb = Math.Clamp(squeezingDb, -15.0, 15.0);
            }

            // 3. 펌프 위상 오차 PI 제어
            double phaseError = TargetPhaseDeg - measuredPhaseDeg;
            _accumulatedPhaseError += phaseError * dt;
            _accumulatedPhaseError = Math.Clamp(_accumulatedPhaseError, -30.0, 30.0);

            double deltaPhase = Kp * phaseError + Ki * _accumulatedPhaseError;
            _currentPumpPhase += deltaPhase * 0.05;

            // 4. 자속 바이어스 미세 드리프트 보정
            if (Math.Abs(phaseError) > 5.0)
            {
                _currentFluxCurrent += Math.Sign(phaseError) * 1e-8; // 나노암페어 미세 트림
            }

            // 5. 큐비트 판독 충실도 추정 (압축도에 비례)
            double fidelity = 0.95 + 0.004 * Math.Max(squeezingDb, 0.0);
            fidelity = Math.Clamp(fidelity, 0.90, 0.999);

            bool isLocked = Math.Abs(phaseError) < 1.5;

            return new JpaControlOutput(
                phaseDeg: _currentPumpPhase,
                fluxCur: _currentFluxCurrent,
                sqDb: squeezingDb,
                fidelity: fidelity,
                isLocked: isLocked
            );
        }
    }
}