论文标题
QREM的多重动力学
Multifractal Dynamics of the QREM
论文作者
论文摘要
我们从数值上研究量子随机能量模型的总体传输方案及其与量子计算的关系,对于$ n \ leq 20 $量子旋转的系统大小。我们专注于能量匹配问题,即当提供已知的近似解决方案作为输入的一部分时,找到组合优化问题的多个近似解决方案。我们通过观察到时间进化波函数的香农熵的饱和度来研究由人口转移方案引起的定位过程,以衡量其在系统上的扩散。该熵在饱和度中的值的缩放随系统的体积鉴定了模型的三个已知动力学阶段。在非共性延长阶段,我们观察到,完成人口转移所需的时间是长尾分布的。我们设计了两个统计数据,以量化协议如何有效,均匀地填充目标能量壳。我们发现,如果选择接近模型的安德森过渡的临界点,人口转移是最有效的。为了评估种群转移作为量子算法的使用,我们与随机搜索进行比较。我们检测到有利于PT的“黑匣子”优势,但是当考虑到人口转移和随机搜索的运行时间时,我们看不到在系统尺寸上可以访问我们的数值方法的速度的强烈指示。我们讨论这些结果以及人口转移对NISQ设备的影响。
We study numerically the population transfer protocol on the Quantum Random Energy Model and its relation to quantum computing, for system sizes of $n\leq 20$ quantum spins. We focus on the energy matching problem, i.e. finding multiple approximate solutions to a combinatorial optimization problem when a known approximate solution is provided as part of the input. We study the delocalization process induced by the population transfer protocol by observing the saturation of the Shannon entropy of the time-evolved wavefunction as a measure of its spread over the system. The scaling of the value of this entropy at saturation with the volume of the system identifies the three known dynamical phases of the model. In the non-ergodic extended phase, we observe that the time necessary for the population transfer to complete follows a long-tailed distribution. We devise two statistics to quantify how effectively and uniformly the protocol populates the target energy shell. We find that population transfer is most effective if the transverse-field parameter $Γ$ is chosen close to the critical point of the Anderson transition of the model. In order to assess the use of population transfer as a quantum algorithm we perform a comparison with random search. We detect a "black box" advantage in favour of PT, but when the running times of population transfer and random search are taken into consideration we do not see strong indications of a speedup at the system sizes that are accessible to our numerical methods. We discuss these results and the impact of population transfer on NISQ devices.