【创新应用】量子纠错相干噪声 θ⁴ 损失标度演示

[sdoygb]

Re-submitted. This supersedes #48, which GitHub permanently closed when its source fork was deleted — a pull request cannot be reopened once its head repository is gone.
Branch and commit are identical to the original.

内容

新增 QECNoise 模块，演示量子纠错码在相干单比特旋转噪声下的 θ⁴ 损失标度律。

• 支持 [[5,1,3]]、[[7,1,3]]、[[9,1,3]]
• 相干旋转噪声：log-log 斜率 ≈ 4
• 随机 Pauli 对照：log-log 斜率 ≈ 2
• 包含单元测试和可运行示例

验证

• python3 example/QECNoise/demo_theta4_scaling.py
• python3 -m pytest test/test_qecnoise.py -q