방사광 X선 극저온 양자 원격전송 리피터 얽힘 스와핑(Entanglement Swapping) BSM 서보 C# SIMD 엔진

3. C# .NET 9.0 Zero-Allocation 50kHz BSM 및 광전변조기(EOM) 제어 엔진

단일 광자 검출 펄스의 나노초 타임스탬프 히스토그램을 메모리 할당 없이 SIMD 레지스터 상에서 직접 누적하고, 능동 광전변조기(EOM) 구동 전압을 산출합니다.

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace ZeliDesk.Quantum.Repeater
{
    /// <summary>
    /// SNSPD 4채널 단일 광자 일치 계수 원시 패킷
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct SinglePhotonCoincidenceBlock
    {
        public readonly long BlockId;
        public readonly double AcquisitionTimestampNs;
        public readonly Vector256<int> ChannelClickCounts; // [D1_H, D1_V, D2_H, D2_V, Coin1, Coin2, Lost, Noise]
        public readonly float InterFerometerPhaseDriftRad;

        public SinglePhotonCoincidenceBlock(long id, double timeNs, Vector256<int> clicks, float phaseDrift)
        {
            BlockId = id;
            AcquisitionTimestampNs = timeNs;
            ChannelClickCounts = clicks;
            InterFerometerPhaseDriftRad = phaseDrift;
        }
    }

    /// <summary>
    /// 50kHz 고속 양자 얽힘 스와핑 BSM 판정 및 EOM 위상 피드백 서보
    /// </summary>
    public sealed class QuantumRepeaterBsmEngine
    {
        private const float TargetFidelity = 0.945f;
        private const float VpiEOMVolts = 3.65f; // EOM 반파장 전압 (V_pi)
        private const float FeedbackKp = 1.15f;
        private const float FeedbackKi = 0.085f;

        private float _accumulatedPhaseError;
        private float _currentEomVoltage;

        public QuantumRepeaterBsmEngine()
        {
            _accumulatedPhaseError = 0.0f;
            _currentEomVoltage = 0.0f;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
        public void ProcessCoincidenceAndCorrectPhase(
            in SinglePhotonCoincidenceBlock block,
            out bool isBellStatePsiMinus,
            out float currentHomVisibility,
            out float estimatedSwappedFidelity,
            out float commandedEomVoltage)
        {
            // 1. 일치 계수 벡터 분해
            Span<int> counts = stackalloc int[8];
            MemoryMarshal.Write(MemoryMarshal.AsBytes(counts), in block.ChannelClickCounts);

            int d1H = counts[0];
            int d2V = counts[3];
            int coincidences = counts[4]; // Psi- 포트 간 일치 계수
            int accidentalCoincidences = counts[5]; // 배경 우연 일치 계수

            // 2. HOM 간섭 가시도(Visibility) 실시간 추정
            int total = coincidences + accidentalCoincidences;
            if (total > 0)
            {
                currentHomVisibility = (float)(coincidences - accidentalCoincidences) / total;
                currentHomVisibility = Math.Clamp(currentHomVisibility, 0.0f, 1.0f);
            }
            else
            {
                currentHomVisibility = 1.0f;
            }

            // 3. 원격 A-D 큐비트 유효 얽힘 충실도 F_AD 계산
            estimatedSwappedFidelity = (1.0f + 3.0f * currentHomVisibility) * 0.25f;

            // 4. 벨 상태 투영 판정 (Psi- 상태 식별)
            isBellStatePsiMinus = (coincidences > 0) && (estimatedSwappedFidelity >= TargetFidelity);

            // 5. 광학 위상 드리프트 실시간 EOM 되먹임 루프 (50kHz)
            float phaseErr = block.InterFerometerPhaseDriftRad;
            _accumulatedPhaseError += phaseErr;

            float deltaV = (FeedbackKp * phaseErr) + (FeedbackKi * _accumulatedPhaseError);
            _currentEomVoltage += (deltaV / MathF.PI) * VpiEOMVolts;

            // EOM 동작 전압 포화 리셋 (-10V ~ +10V)
            if (_currentEomVoltage > 10.0f) _currentEomVoltage -= 2.0f * VpiEOMVolts;
            if (_currentEomVoltage < -10.0f) _currentEomVoltage += 2.0f * VpiEOMVolts;

            commandedEomVoltage = _currentEomVoltage;
        }
    }
}