新型半导体杂化量子比特动力学解耦研究

To achieve the quantum operation as much as possible in the coherence time is one of the key issues to realize the quantum computation. Hybrid qubit, one of the proposals that attempt to address this issue, has been proposed recently. Our recent experiments have improved and optimized this hybrid qubit. We demonstrate a highly tunable hybrid qubit with fast operation and long coherence time in a GaAs heterostructure. However, decoherence of the hybrid qubit arises from the interaction between the qubit and the uncontrolled environment. In this project, we intend to enhance the coherent time using dynamical-decoupling techniques by applying high frequency pulse sequences to filter the specific noise of the environment. The dynamical-decoupling techniques will also help us to study the environmental noise spectrum which can help us improve and optimize the hybrid qubit further. This project will focus on the hybrid qubit, which is a new type qubit. And it will pave a new way for future quantum computation. More importantly, the project will develop the high frequency control techniques which will be an asset for the development of the quantum computation.

在量子比特相干时间内尽可能多的完成量子操控是实现量子计算的核心问题之一。近期提出的半导体杂化量子比特因能兼容操控速度、相干时间这一核心问题而受到广泛关注。我们最近的实验成果进一步改进和优化了这种编码方式，在GaAs体系中得到了兼具超快操控与长相干时间优良特性的新型杂化量子比特。进一步，如果能抑制周围环境噪声，该比特将具有更长的相干时间。本项目拟在近期实验成果基础上，利用动力学解耦，对量子比特施加高频序列信号，消除比特与周围噪声环境的耦合，提高比特相干时间；同时，利用动力学解耦波形对特定噪声频段敏感的特性，系统分析与研究该新型量子比特的消相干机制，进一步优化与改进杂化量子比特编码。项目针对杂化量子比特这一全新编码方式的量子比特展开，将为未来量子计算的发展探索新的思路；更为重要的是，项目实施过程中开发出来的皮秒量级复杂高频序列电信号操控技术，将为未来半导体量子计算提供重要技术积累。

在量子比特相干时间内尽可能多的完成量子操控是实现量子计算的核心问题之一。通过动力学解耦过程可以很好地抑制量子比特周围环境噪声，大幅提升量子比特退相干时间。本项目实施过程中系统发展了高频操控技术，对量子比特施加高频序列信号，利用动力学解耦过程将电荷量子比特退相干时间从<120皮秒提升到>1300皮秒，将空穴自旋比特退相干时间从250纳秒提升到520纳秒。项目实施过程中开发出来的皮秒量级高频序列电信号操控技术，将为未来半导体量子计算提供重要技术积累。与此同时，项目还在多比特集成方面做了积极探索，实现了半导体三量子比特静态Toffoli门演示，实现了微波谐振腔与半导体量子比特强耦合，并利用微波谐振腔实现了两量子比特长程耦合。