简并量子系统中扰动的传播
Propagation of Disturbances in Degenerate Quantum Systems
摘要：
无间隙量子多体模型中的扰动在整个系统中传播的距离是无限的。在这里，我们探讨这一现象在有限集团与简并基态。这里研究的具体模型是一维J1-J2海森堡哈密顿量在和接近Majumdar-Ghosh点。考虑了开边界条件和周期边界条件。使用局部磁场进行猝灭。简并的Majumdar-Ghosh基态允许携带量子纠缠的扰动在整个系统中传播，从而使整个系统在简并子空间内退相。这些扰动也可以携带极化，但不是能量，因为所有能量都存储在本地。系统中储存能量的部分的局部演化通过长程纠缠驱动系统的其余部分。我们还研究了近似的基态的这个哈密顿量在强场的限制，并研究如何耦合远离Majumdar-Ghosh点影响传播的干扰。我们发现，即使在近似退化的情况下，扰动可以传播到整个有限系统。
英文摘要：
Disturbances in gapless quantum many-body models are known to travel an unlimited distance throughout the system. Here, we explore this phenomenon in finite clusters with degenerate ground states. The specific model studied here is the one-dimensional J1-J2 Heisenberg Hamiltonian at and close to the Majumdar-Ghosh point. Both open and periodic boundary conditions are considered. Quenches are performed using a local magnetic field. The degenerate Majumdar-Ghosh ground state allows disturbances which carry quantum entanglement to propagate throughout the system, and thus dephase the entire system within the degenerate subspace. These disturbances can also carry polarization, but not energy, as all energy is stored locally. The local evolution of the part of the system where energy is stored drives the rest of the system through long-range entanglement. We also examine approximations for the ground state of this Hamiltonian in the strong field limit, and study how couplings away from the Majumdar-Ghosh point affect the propagation of disturbances. We find that even in the case of approximate degeneracy, a disturbance can be propagated throughout a finite system.
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