论文标题
自旋系统中动态隧道的NMR研究
NMR investigations of Dynamical Tunneling in Spin Systems
论文作者
论文摘要
在通常的量子隧道中，低能量子粒子通过穿越经典的禁区，并最终逃脱到另一个区域，从而穿过较高势能的物理屏障。在类似的情况下，相位空间中封闭的常规区域内的经典粒子是从逃逸到相空间的其他区域的动态结合的。在这里，物理潜在的屏障被动态障碍所取代，这些障碍物将相位空间的不同区域分开。但是，在量子状态下，系统可以克服这种动态障碍并通过它们逃脱，从而导致动态隧道。在混乱的哈密顿系统中，动态隧道是指经典极限对应于与对称性相关的常规区域之间的量子隧道，该区域被禁止任何经典运输之间的混乱区分开。在这里，使用核磁共振（NMR）结构报告了自旋系统中动态隧道的实验实现。特别是，研究了使用两量和三Q量的NMR寄存器中量子踢的动力学隧道踢到Spin-1和Spin-3/2系统的顶部。通过提取角动量算子组件的时间依赖性期望值，可以系统地研究各种初始状态的尺寸依赖性隧道行为。此外，通过监测噪声对隧道振荡的不利影响，我们断言量子相干性在启用动态隧道中的重要性。
In the usual quantum tunneling, a low-energy quantum particle penetrates across a physical barrier of higher potential energy, by traversing a classically forbidden region, and finally escapes into another region. In an analogous scenario, a classical particle inside a closed regular region in the phase space is dynamically bound from escaping to other regions of the phase space. Here, the physical potential barrier is replaced by dynamical barriers which separate different regions of the phase space. However, in the quantum regime, the system can overcome such dynamical barriers and escape through them, giving rise to dynamical tunneling. In chaotic Hamiltonian systems, dynamical tunneling refers to quantum tunneling between states whose classical limit correspond to symmetry-related regular regions separated by a chaotic zone between which any classical transport is prohibited. Here, an experimental realization of dynamical tunneling in spin systems is reported using nuclear magnetic resonance (NMR) architecture. In particular, dynamical tunneling in quantum kicked tops of spin-1 and spin-3/2 systems using two- and three-qubit NMR registers is investigated. By extracting time-dependent expectation values of the angular momentum operator components, size-dependent tunneling behaviour for various initial states is systematically investigated. Further, by monitoring the adverse effects of dephasing noise on the tunneling oscillations, we assert the importance of quantum coherence in enabling dynamical tunneling.
