论文标题
通过Bang-Bang协议的超快关键基础状态准备
Ultrafast critical ground state preparation via bang-bang protocols
论文作者
论文摘要
量子系统的基础状态的快速而忠实的准备是一项具有挑战性的任务，但对于基于量子的技术领域的几种应用至关重要。矫正对允许实验的最大时间窗口构成了限制，以忠实地实现此类所需的状态。这在关键系统中尤其重要，在关键系统中，消失的能量差距挑战了绝热的基态制备。我们表明，由在两个不同的外部可调参数的两个不同值下的时间演化组成的BANG-BANG协议允许在进化时间中进行高保真地基态制备，而不必应用标准最佳控制技术所需的时间，例如切碎的范围基础基础基础量子优化。此外，由于它们的变量数量减少，因此这种Bang-Bang协议非常适合优化目的，从而降低了其他最佳控制协议的计算成本的增加。我们通过两个范式模型（即Landau-Zener和Lipkin-Meshkov-Glick型号）基准了这种方法的性能。值得注意的是，后一种模型的临界基态可以在总进化时间内以高忠诚度制备，比消失的能量间隙的倒数较慢。
The fast and faithful preparation of the ground state of quantum systems is a challenging task but crucial for several applications in the realm of quantum-based technologies. Decoherence poses a limit to the maximum time-window allowed to an experiment to faithfully achieve such desired states. This is of particular significance in critical systems, where the vanishing energy gap challenges an adiabatic ground state preparation. We show that a bang-bang protocol, consisting of a time evolution under two different values of an externally tunable parameter, allows for a high-fidelity ground state preparation in evolution times no longer than those required by the application of standard optimal control techniques, such as the chopped-random basis quantum optimization. In addition, owing to their reduced number of variables, such bang-bang protocols are very well suited to optimization purposes, reducing the increasing computational cost of other optimal control protocols. We benchmark the performance of such approach through two paradigmatic models, namely the Landau-Zener and the Lipkin-Meshkov-Glick model. Remarkably, the critical ground state of the latter model can be prepared with a high fidelity in a total evolution time that scales slower than the inverse of the vanishing energy gap.
