When a qubit or spin interacts with others under a many-body Hamiltonian, the information it contains progressively scrambles. Here, nuclear spins of an adamantane crystal are used as a quantum simulator to monitor such dynamics through out-of-time-order correlators, while a Loschmidt echo (LE) asses how weak perturbations degrade the information encoded in these increasingly complex states. Both observables involve the implementation of a time-reversal procedure which, in practice, involves inverting the sign of the effective Hamiltonian. Our protocols use periodic radio frequency pulses to modulate the natural dipolar interaction implementing a Hamiltonian that can be scaled down at will. Meanwhile, experimental errors and strength of perturbative terms remain constant and can be quantified through the LE. For each scaling factor, information spreading occurs with a timescale, T_{2}, inversely proportional to the local second moment of the Hamiltonian. We find that, when the reversible interactions dominate over the perturbations, the information scrambled among up to 10^{2} spins can still be recovered. However, we find that the LE decay rate cannot become smaller than a critical value 1/T_{3}≈(0.15±0.02)/T_{2}, which only depends on the interactions themselves, and not on the perturbations. This result shows the emergence of a regime of intrinsic irreversibility in accordance to a central hypothesis of irreversibility, hinted from previous experiments.

中文翻译：

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Lossmidt回声在多体系统中的独立于摄动的衰减。

当一个量子位或自旋在多体哈密顿量下与他人相互作用时，它包含的信息将逐渐加扰。在这里，金刚烷晶体的核自旋被用作量子模拟器，以通过无序的相关器来监视这种动态，而洛施密特回波（LE）则评估了微弱的扰动如何使这些日益复杂的状态下编码的信息退化。这两个可观察值都涉及时间倒转过程的实施，实际上，这需要反转有效哈密顿量的符号。我们的协议使用周期性的射频脉冲来调制自然的偶极相互作用，从而实现可以任意缩减的哈密顿量。同时，实验误差和微扰项的强度保持恒定，可以通过LE进行量化。对于每个比例因子，信息传播发生在时间尺度T_ {2}上，该时间尺度与哈密顿量的局部第二矩成反比。我们发现，当可逆相互作用在扰动中占主导地位时，仍然可以恢复在10 ^ {2}个自旋中扰乱的信息。然而，我们发现LE衰减率不能变得小于临界值1 / T_ {3}≈（0.15±0.02）/ T_ {2}，该临界值仅取决于相互作用本身，而不取决于扰动。该结果表明，根据先前实验的暗示，根据不可逆性的中心假设出现了内在不可逆性制度。仍然可以恢复在多达10 ^ {2}个自旋中加扰的信息。但是，我们发现LE衰减率不能小于临界值1 / T_ {3}≈（0.15±0.02）/ T_ {2}，该临界值仅取决于相互作用本身，而不取决于扰动。该结果表明，根据先前实验的暗示，根据不可逆性的中心假设出现了内在不可逆性制度。仍然可以恢复在多达10 ^ {2}个自旋中加扰的信息。然而，我们发现LE衰减率不能变得小于临界值1 / T_ {3}≈（0.15±0.02）/ T_ {2}，该临界值仅取决于相互作用本身，而不取决于扰动。该结果表明，根据先前实验的暗示，根据不可逆性的中心假设出现了内在不可逆性制度。