Quantum information scrambling is a unitary process that destroys local correlations and spreads information throughout the system, effectively hiding it in nonlocal degrees of freedom. In principle, unscrambling this information is possible with perfect knowledge of the unitary dynamics [B. Yoshida and A. Kitaev, arXiv:1710.03363.]. However, this Letter demonstrates that even without previous knowledge of the internal dynamics, information can be efficiently decoded from an unknown scrambler by monitoring the outgoing information of a local subsystem. Surprisingly, we show that scramblers with unknown internal dynamics, which are rapidly mixing but not fully chaotic, can be decoded using Clifford decoders. The essential properties of a scrambling unitary can be efficiently recovered, even if the process is exponentially complex. Specifically, we establish that a unitary operator composed of $t$ non-Clifford gates admits a Clifford decoder up to $t\le n$.

翻译：量子信息混沌化是一个酉过程，它破坏局部关联并将信息扩散至整个系统，有效地将其隐藏在非局部自由度中。理论上，若对酉动力学有完全了解，则可能解谜这些信息[B. Yoshida 和 A. Kitaev, arXiv:1710.03363]。然而，本论文证明，即使对内部动力学缺乏先验知识，通过监测局部子系统的输出信息，也能从未知的混沌化器中高效解码信息。令人惊讶的是，我们表明，具有未知内部动力学、快速混合但非完全混沌的混沌化器，可使用克利福德解码器进行解码。即便过程呈指数级复杂，混沌化酉算子的基本属性也能被高效恢复。具体而言，我们确定一个由$t$个非克利福德门构成的酉算子，在$t\le n$时允许一个克利福德解码器。