Single-shot Landau-Zener-Stückelberg experiment

量子退火法(QA)是一种传统的绝热优化方法，非绝热量子退火法(AQA)逐渐改变哈密顿量，使系统始终处于哈密顿量的瞬时基态。然而，这一缓慢的过程可能会阻碍计算加速。相反，非绝热量子退火(DQA)允许在退火过程中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，理论上证明了量子比特在进行DQA时表现出的干涉效应相当于单次通过Landau-Zener-Stuckelberg(LZS)干涉仪。然而，这个实验还没有实现。这个项目的目的是在高Q超导磁通量子比特上进行单发LZS实验。我们的目标是利用LZS跃迁的干扰效应作为绝热的捷径。此外，我们可以利用干涉效应来研究量子比特的退相干，这强烈地依赖于与环境的相互作用。这项实验需要高水平的实验控制。在项目期间开发的工具和技术将是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.