Lee Wonjun, Kwon Hyukjoon, Cho Gil Young
Department of Physics, Pohang University of Science and Technology, Pohang, South Korea.
Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang, South Korea.
Nat Commun. 2025 Jul 23;16(1):6800. doi: 10.1038/s41467-025-62081-6.
Quantum chaos is central to understanding quantum dynamics and is crucial for generating random quantum states, a key resource for quantum information tasks. In this work, we introduce a new class of quantum many-body dynamics, termed pseudochaotic dynamics. Although distinct from chaotic dynamics, out-of-time-ordered correlators, the key indicators of quantum chaos, fail to distinguish them. Moreover, pseudochaotic dynamics generates pseudorandom states that are computationally indistinguishable from Haar-random states. We construct pseudochaotic dynamics by embedding a smaller k-qubit subsystem into a larger n-qubit system. We demonstrate that a subsystem of size is sufficient to induce pseudochaotic behavior in the entire n-qubit system. Furthermore, we construct a quantum circuit exhibiting pseudochaotic dynamics and demonstrate that it generates pseudorandom states within depth. In summary, our results constitute the discovery of new quantum dynamics that are computationally indistinguishable from genuine quantum chaos, which provides efficient routes to generate useful pseudorandom states.
量子混沌是理解量子动力学的核心，对于生成随机量子态至关重要，而随机量子态是量子信息任务的关键资源。在这项工作中，我们引入了一类新的量子多体动力学，称为伪混沌动力学。尽管它与混沌动力学不同，但量子混沌的关键指标——时间反序关联函数却无法区分它们。此外，伪混沌动力学生成的伪随机态在计算上与哈尔随机态无法区分。我们通过将一个较小的k量子比特子系统嵌入到一个较大的n量子比特系统中来构建伪混沌动力学。我们证明，大小为 的子系统足以在整个n量子比特系统中诱导出伪混沌行为。此外，我们构建了一个表现出伪混沌动力学的量子电路，并证明它能在 深度内生成伪随机态。总之，我们的结果构成了对新量子动力学的发现，这些动力学在计算上与真正的量子混沌无法区分，这为生成有用的伪随机态提供了有效途径。
