Single-shot Landau-Zener-Stückelberg experiment

量子退火（QA）是一种传统的绝热优化方法，绝热量子退火（AQA）逐渐改变系统的哈密顿量，使系统始终处于哈密顿量的瞬时基态。然而，这种缓慢的过程可能会妨碍计算加速。相比之下，非绝热量子退火（DQA）允许在退火期间基态和激发态之间的跃迁。因此，退火过程可以花费更少的时间，从而实现量子加速。最近，理论上已经证明，经历DQA的量子比特表现出相当于单次通过Landau-Zener-Stuckelberg（LZS）干涉仪的干涉效应。然而，该实验尚未实现。该项目旨在对高Q超导磁通量子比特进行单次LZS实验。我们的目标是利用LZS转变的干涉效应作为绝热性的捷径。此外，我们可以使用干涉效应来研究量子比特的退相干，这在很大程度上取决于与环境的相互作用。这个实验需要高水平的实验控制。项目期间开发的工具和技术将成为DQA研究的基础。

Quantum annealing (QA) is an optimization method conventionally performed in an adiabatic manner.Adiabatic quantum annealing (AQA) gradually changes the Hamiltonian so that the system stays in an instantaneous ground state of the Hamiltonian at all times. However, this slow process could hamper computational speedup. In contrast, diabatic quantum annealing (DQA) allows transitions between the ground state and excited states during the anneal. Hence the annealing process can take less time, enabling quantum speedup. Recently it has been theoretically demonstrated that a qubit undergoing DQA exhibits an interference effect equivalent to a single pass through a Landau-Zener-Stuckelberg (LZS) interferometer. Nevertheless, the experiment has not been realized. This project aims to perform a single-shot LZS experiment on a high-Q superconducting flux qubit. Our goal is to exploit the interference effect from the LZS transition as a shortcut to adiabaticity. Furthermore we can use the interference effect to investigate qubit decoherence, which strongly depends on interactions with the environment. This experiment demands a high level of experimental control. The tools and techniques developed during the project will be the basis for research towards DQA.